diff --git a/libc/tzcode/asctime.c b/libc/tzcode/asctime.c
index ce5d4be..4cdfd13 100644
--- a/libc/tzcode/asctime.c
+++ b/libc/tzcode/asctime.c
@@ -17,12 +17,6 @@
 #include <stdio.h>
 
 /*
-** Some systems only handle "%.2d"; others only handle "%02d";
-** "%02.2d" makes (most) everybody happy.
-** At least some versions of gcc warn about the %02.2d;
-** we conditionalize below to avoid the warning.
-*/
-/*
 ** All years associated with 32-bit time_t values are exactly four digits long;
 ** some years associated with 64-bit time_t values are not.
 ** Vintage programs are coded for years that are always four digits long
@@ -34,24 +28,16 @@
 ** The ISO C and POSIX standards prohibit padding the year,
 ** but many implementations pad anyway; most likely the standards are buggy.
 */
-#ifdef __GNUC__
-#define ASCTIME_FMT	"%s %s%3d %2.2d:%2.2d:%2.2d %-4s\n"
-#else /* !defined __GNUC__ */
-#define ASCTIME_FMT	"%s %s%3d %02.2d:%02.2d:%02.2d %-4s\n"
-#endif /* !defined __GNUC__ */
+static char const ASCTIME_FMT[] = "%s %s%3d %.2d:%.2d:%.2d %-4s\n";
 /*
 ** For years that are more than four digits we put extra spaces before the year
 ** so that code trying to overwrite the newline won't end up overwriting
 ** a digit within a year and truncating the year (operating on the assumption
 ** that no output is better than wrong output).
 */
-#ifdef __GNUC__
-#define ASCTIME_FMT_B	"%s %s%3d %2.2d:%2.2d:%2.2d     %s\n"
-#else /* !defined __GNUC__ */
-#define ASCTIME_FMT_B	"%s %s%3d %02.2d:%02.2d:%02.2d     %s\n"
-#endif /* !defined __GNUC__ */
+static char const ASCTIME_FMT_B[] = "%s %s%3d %.2d:%.2d:%.2d     %s\n";
 
-#define STD_ASCTIME_BUF_SIZE	26
+enum { STD_ASCTIME_BUF_SIZE = 26 };
 /*
 ** Big enough for something such as
 ** ??? ???-2147483648 -2147483648:-2147483648:-2147483648     -2147483648\n
@@ -59,15 +45,23 @@
 ** seven explicit spaces, two explicit colons, a newline,
 ** and a trailing NUL byte).
 ** The values above are for systems where an int is 32 bits and are provided
-** as an example; the define below calculates the maximum for the system at
+** as an example; the size expression below is a bound for the system at
 ** hand.
 */
-#define MAX_ASCTIME_BUF_SIZE	(2*3+5*INT_STRLEN_MAXIMUM(int)+7+2+1+1)
+static char buf_asctime[2*3 + 5*INT_STRLEN_MAXIMUM(int) + 7 + 2 + 1 + 1];
 
-static char	buf_asctime[MAX_ASCTIME_BUF_SIZE];
+/* A similar buffer for ctime.
+   C89 requires that they be the same buffer.
+   This requirement was removed in C99, so support it only if requested,
+   as support is more likely to lead to bugs in badly written programs.  */
+#if SUPPORT_C89
+# define buf_ctime buf_asctime
+#else
+static char buf_ctime[sizeof buf_asctime];
+#endif
 
 char *
-asctime_r(register const struct tm *timeptr, char *buf)
+asctime_r(struct tm const *restrict timeptr, char *restrict buf)
 {
 	static const char	wday_name[][4] = {
 		"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
@@ -79,7 +73,7 @@
 	register const char *	wn;
 	register const char *	mn;
 	char			year[INT_STRLEN_MAXIMUM(int) + 2];
-	char			result[MAX_ASCTIME_BUF_SIZE];
+	char result[sizeof buf_asctime];
 
 	if (timeptr == NULL) {
 		errno = EINVAL;
@@ -107,7 +101,8 @@
 		timeptr->tm_mday, timeptr->tm_hour,
 		timeptr->tm_min, timeptr->tm_sec,
 		year);
-	if (strlen(result) < STD_ASCTIME_BUF_SIZE || buf == buf_asctime)
+	if (strlen(result) < STD_ASCTIME_BUF_SIZE
+	    || buf == buf_ctime || buf == buf_asctime)
 		return strcpy(buf, result);
 	else {
 		errno = EOVERFLOW;
@@ -120,3 +115,17 @@
 {
 	return asctime_r(timeptr, buf_asctime);
 }
+
+char *
+ctime_r(const time_t *timep, char *buf)
+{
+  struct tm mytm;
+  struct tm *tmp = localtime_r(timep, &mytm);
+  return tmp ? asctime_r(tmp, buf) : NULL;
+}
+
+char *
+ctime(const time_t *timep)
+{
+  return ctime_r(timep, buf_ctime);
+}
diff --git a/libc/tzcode/localtime.c b/libc/tzcode/localtime.c
index 8ff5cee..5e1181f 100644
--- a/libc/tzcode/localtime.c
+++ b/libc/tzcode/localtime.c
@@ -28,29 +28,22 @@
 static void unlock(void) { }
 #endif
 
-#ifndef TZ_ABBR_MAX_LEN
-#define TZ_ABBR_MAX_LEN 16
-#endif /* !defined TZ_ABBR_MAX_LEN */
-
 #ifndef TZ_ABBR_CHAR_SET
-#define TZ_ABBR_CHAR_SET \
+# define TZ_ABBR_CHAR_SET \
     "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 :+-._"
 #endif /* !defined TZ_ABBR_CHAR_SET */
 
 #ifndef TZ_ABBR_ERR_CHAR
-#define TZ_ABBR_ERR_CHAR    '_'
+# define TZ_ABBR_ERR_CHAR    '_'
 #endif /* !defined TZ_ABBR_ERR_CHAR */
 
 /*
-** SunOS 4.1.1 headers lack O_BINARY.
++** Support non-POSIX platforms that distinguish between text and binary files.
 */
 
-#ifdef O_BINARY
-#define OPEN_MODE   (O_RDONLY | O_BINARY)
-#endif /* defined O_BINARY */
 #ifndef O_BINARY
-#define OPEN_MODE   O_RDONLY
-#endif /* !defined O_BINARY */
+# define O_BINARY 0
+#endif
 
 #ifndef WILDABBR
 /*
@@ -72,12 +65,13 @@
 ** manual page of what this "time zone abbreviation" means (doing this so
 ** that tzname[0] has the "normal" length of three characters).
 */
-#define WILDABBR    "   "
+# define WILDABBR    "   "
 #endif /* !defined WILDABBR */
 
 static const char       wildabbr[] = WILDABBR;
 
-static const char gmt[] = "GMT";
+static char const etc_utc[] = "Etc/UTC";
+static char const *utc = etc_utc + sizeof "Etc/" - 1;
 
 /*
 ** The DST rules to use if TZ has no rules and we can't load TZDEFRULES.
@@ -86,7 +80,7 @@
 ** for historical reasons, US rules are a common default.
 */
 #ifndef TZDEFRULESTRING
-#define TZDEFRULESTRING ",M3.2.0,M11.1.0"
+# define TZDEFRULESTRING ",M3.2.0,M11.1.0"
 #endif
 
 struct ttinfo {              /* time type information */
@@ -102,9 +96,6 @@
     int_fast32_t ls_corr;    /* correction to apply */
 };
 
-#define SMALLEST(a, b)	(((a) < (b)) ? (a) : (b))
-#define BIGGEST(a, b)   (((a) > (b)) ? (a) : (b))
-
 /* This abbreviation means local time is unspecified.  */
 static char const UNSPEC[] = "-00";
 
@@ -112,14 +103,13 @@
    This needs to be at least 1 for null termination in case the input
    data isn't properly terminated, and it also needs to be big enough
    for ttunspecified to work without crashing.  */
-enum { CHARS_EXTRA = BIGGEST(sizeof UNSPEC, 2) - 1 };
+enum { CHARS_EXTRA = max(sizeof UNSPEC, 2) - 1 };
 
-#ifdef TZNAME_MAX
-#define MY_TZNAME_MAX   TZNAME_MAX
-#endif /* defined TZNAME_MAX */
-#ifndef TZNAME_MAX
-#define MY_TZNAME_MAX   255
-#endif /* !defined TZNAME_MAX */
+/* Limit to time zone abbreviation length in POSIX-style TZ strings.
+   This is distinct from TZ_MAX_CHARS, which limits TZif file contents.  */
+#ifndef TZNAME_MAXIMUM
+# define TZNAME_MAXIMUM 255
+#endif
 
 struct state {
     int           leapcnt;
@@ -131,9 +121,8 @@
     time_t        ats[TZ_MAX_TIMES];
     unsigned char types[TZ_MAX_TIMES];
     struct ttinfo ttis[TZ_MAX_TYPES];
-    char          chars[BIGGEST(BIGGEST(TZ_MAX_CHARS + CHARS_EXTRA,
-                            sizeof gmt),
-                  (2 * (MY_TZNAME_MAX + 1)))];
+    char chars[max(max(TZ_MAX_CHARS + CHARS_EXTRA, sizeof "UTC"),
+		         2 * (TZNAME_MAXIMUM + 1))];
     struct lsinfo lsis[TZ_MAX_LEAPS];
     /* The time type to use for early times or if no transitions.
        It is always zero for recent tzdb releases.
@@ -174,12 +163,12 @@
 #ifndef ALL_STATE
 static struct state lclmem;
 static struct state gmtmem;
-#define lclptr      (&lclmem)
-#define gmtptr      (&gmtmem)
+static struct state *const lclptr = &lclmem;
+static struct state *const gmtptr = &gmtmem;
 #endif /* State Farm */
 
 #ifndef TZ_STRLEN_MAX
-#define TZ_STRLEN_MAX 255
+# define TZ_STRLEN_MAX 255
 #endif /* !defined TZ_STRLEN_MAX */
 
 static char lcl_TZname[TZ_STRLEN_MAX + 1];
@@ -191,9 +180,14 @@
 **  ctime, gmtime, localtime] return values in one of two static
 **  objects: a broken-down time structure and an array of char.
 ** Thanks to Paul Eggert for noting this.
+**
+** This requirement was removed in C99, so support it only if requested,
+** as support is more likely to lead to bugs in badly written programs.
 */
 
+#if SUPPORT_C89
 static struct tm	tm;
+#endif
 
 #if 2 <= HAVE_TZNAME + TZ_TIME_T
 char *			tzname[2] = {
@@ -321,7 +315,7 @@
 	int stddst_mask = 0;
 
 #if HAVE_TZNAME
-	tzname[0] = tzname[1] = (char *) (sp ? wildabbr : gmt);
+	tzname[0] = tzname[1] = (char *) (sp ? wildabbr : utc);
 	stddst_mask = 3;
 #endif
 #if USG_COMPAT
@@ -346,27 +340,28 @@
 #endif
 }
 
-static void
+/* Replace bogus characters in time zone abbreviations.
+   Return 0 on success, an errno value if a time zone abbreviation is
+   too long.  */
+static int
 scrub_abbrs(struct state *sp)
 {
 	int i;
-	/*
-	** First, replace bogus characters.
-	*/
+
+	/* Reject overlong abbreviations.  */
+	for (i = 0; i < sp->charcnt - (TZNAME_MAXIMUM + 1); ) {
+	  int len = strlen(&sp->chars[i]);
+	  if (TZNAME_MAXIMUM < len)
+	    return EOVERFLOW;
+	  i += len + 1;
+	}
+
+	/* Replace bogus characters.  */
 	for (i = 0; i < sp->charcnt; ++i)
 		if (strchr(TZ_ABBR_CHAR_SET, sp->chars[i]) == NULL)
 			sp->chars[i] = TZ_ABBR_ERR_CHAR;
-	/*
-	** Second, truncate long abbreviations.
-	*/
-	for (i = 0; i < sp->typecnt; ++i) {
-		register const struct ttinfo * const	ttisp = &sp->ttis[i];
-		char *cp = &sp->chars[ttisp->tt_desigidx];
 
-		if (strlen(cp) > TZ_ABBR_MAX_LEN &&
-			strcmp(cp, GRANDPARENTED) != 0)
-				*(cp + TZ_ABBR_MAX_LEN) = '\0';
-	}
+	return 0;
 }
 
 /* Input buffer for data read from a compiled tz file.  */
@@ -399,8 +394,7 @@
   // Android-removed: There is no directory with file-per-time zone on Android.
   #ifndef __BIONIC__
   /* The file name to be opened.  */
-  char fullname[BIGGEST(sizeof(struct file_analysis),
-      sizeof tzdirslash + 1024)];
+  char fullname[max(sizeof(struct file_analysis), sizeof tzdirslash + 1024)];
   #endif
 };
 
@@ -446,8 +440,7 @@
 #endif
 	if (!doaccess) {
 		char const *dot;
-		size_t namelen = strlen(name);
-		if (sizeof lsp->fullname - sizeof tzdirslash <= namelen)
+		if (sizeof lsp->fullname - sizeof tzdirslash <= strlen(name))
 		  return ENAMETOOLONG;
 
 		/* Create a string "TZDIR/NAME".  Using sprintf here
@@ -470,7 +463,7 @@
 	}
 	if (doaccess && access(name, R_OK) != 0)
 	  return errno;
-	fid = open(name, OPEN_MODE);
+  fid = open(name, O_RDONLY | O_BINARY);
 #endif
 	if (fid < 0)
 	  return errno;
@@ -828,12 +821,14 @@
 		b < 0 || b >= sp->typecnt)
 			result = false;
 	else {
+		/* Compare the relevant members of *AP and *BP.
+		   Ignore tt_ttisstd and tt_ttisut, as they are
+		   irrelevant now and counting them could cause
+		   sp->goahead to mistakenly remain false.  */
 		register const struct ttinfo *	ap = &sp->ttis[a];
 		register const struct ttinfo *	bp = &sp->ttis[b];
 		result = (ap->tt_utoff == bp->tt_utoff
 			  && ap->tt_isdst == bp->tt_isdst
-			  && ap->tt_ttisstd == bp->tt_ttisstd
-			  && ap->tt_ttisut == bp->tt_ttisut
 			  && (strcmp(&sp->chars[ap->tt_desigidx],
 				     &sp->chars[bp->tt_desigidx])
 			      == 0));
@@ -863,7 +858,7 @@
 ** Return a pointer to that character.
 */
 
-static ATTRIBUTE_PURE const char *
+ATTRIBUTE_REPRODUCIBLE static const char *
 getzname(register const char *strp)
 {
 	register char	c;
@@ -884,7 +879,7 @@
 ** We don't do any checking here; checking is done later in common-case code.
 */
 
-static ATTRIBUTE_PURE const char *
+ATTRIBUTE_REPRODUCIBLE static const char *
 getqzname(register const char *strp, const int delim)
 {
 	register int	c;
@@ -1122,7 +1117,7 @@
             value += mon_lengths[leapyear][i] * SECSPERDAY;
         break;
 
-        default: UNREACHABLE();
+        default: unreachable();
     }
 
     /*
@@ -1144,13 +1139,11 @@
 {
 	const char *			stdname;
 	const char *			dstname;
-	size_t				stdlen;
-	size_t				dstlen;
-	size_t				charcnt;
 	int_fast32_t			stdoffset;
 	int_fast32_t			dstoffset;
 	register char *			cp;
 	register bool			load_ok;
+	ptrdiff_t stdlen, dstlen, charcnt;
 	time_t atlo = TIME_T_MIN, leaplo = TIME_T_MIN;
 
 	stdname = name;
@@ -1166,14 +1159,12 @@
 	  name = getzname(name);
 	  stdlen = name - stdname;
 	}
-	if (!stdlen)
+	if (! (0 < stdlen && stdlen <= TZNAME_MAXIMUM))
 	  return false;
 	name = getoffset(name, &stdoffset);
 	if (name == NULL)
 	  return false;
 	charcnt = stdlen + 1;
-	if (sizeof sp->chars < charcnt)
-	  return false;
 	if (basep) {
 	  if (0 < basep->timecnt)
 	    atlo = basep->ats[basep->timecnt - 1];
@@ -1200,11 +1191,9 @@
 			name = getzname(name);
 			dstlen = name - dstname; /* length of DST abbr. */
 		}
-		if (!dstlen)
+		if (! (0 < dstlen && dstlen <= TZNAME_MAXIMUM))
 		  return false;
 		charcnt += dstlen + 1;
-		if (sizeof sp->chars < charcnt)
-		  return false;
 		if (*name != '\0' && *name != ',' && *name != ';') {
 			name = getoffset(name, &dstoffset);
 			if (name == NULL)
@@ -1420,8 +1409,8 @@
 static void
 gmtload(struct state *const sp)
 {
-	if (tzload(gmt, sp, true) != 0)
-	  tzparse("GMT0", sp, NULL);
+	if (tzload(etc_utc, sp, true) != 0)
+	  tzparse("UTC0", sp, NULL);
 }
 
 /* Initialize *SP to a value appropriate for the TZ setting NAME.
@@ -1439,7 +1428,7 @@
     sp->charcnt = 0;
     sp->goback = sp->goahead = false;
     init_ttinfo(&sp->ttis[0], 0, false, 0);
-    strcpy(sp->chars, gmt);
+    strcpy(sp->chars, utc);
     sp->defaulttype = 0;
     return 0;
   } else {
@@ -1447,7 +1436,7 @@
     if (err != 0 && name && name[0] != ':' && tzparse(name, sp, NULL))
       err = 0;
     if (err == 0)
-      scrub_abbrs(sp);
+      err = scrub_abbrs(sp);
     return err;
   }
 }
@@ -1557,7 +1546,7 @@
 ** set the applicable parts of tzname, timezone and altzone;
 ** however, it's OK to omit this step if the timezone is POSIX-compatible,
 ** since in that case tzset should have already done this step correctly.
-** SETNAME's type is intfast32_t for compatibility with gmtsub,
+** SETNAME's type is int_fast32_t for compatibility with gmtsub,
 ** but it is actually a boolean and its value should be 0 or 1.
 */
 
@@ -1601,6 +1590,14 @@
 					return NULL;	/* "cannot happen" */
 			result = localsub(sp, &newt, setname, tmp);
 			if (result) {
+#if defined ckd_add && defined ckd_sub
+				if (t < sp->ats[0]
+				    ? ckd_sub(&result->tm_year,
+					      result->tm_year, years)
+				    : ckd_add(&result->tm_year,
+					      result->tm_year, years))
+				  return NULL;
+#else
 				register int_fast64_t newy;
 
 				newy = result->tm_year;
@@ -1610,6 +1607,7 @@
 				if (! (INT_MIN <= newy && newy <= INT_MAX))
 					return NULL;
 				result->tm_year = newy;
+#endif
 			}
 			return result;
 	}
@@ -1650,7 +1648,8 @@
 #if NETBSD_INSPIRED
 
 struct tm *
-localtime_rz(struct state *sp, time_t const *timep, struct tm *tmp)
+localtime_rz(struct state *restrict sp, time_t const *restrict timep,
+	     struct tm *restrict tmp)
 {
   return localsub(sp, timep, 0, tmp);
 }
@@ -1681,11 +1680,14 @@
 struct tm *
 localtime(const time_t *timep)
 {
+#if !SUPPORT_C89
+  static struct tm tm;
+#endif
   return localtime_tzset(timep, &tm);
 }
 
 struct tm *
-localtime_r(const time_t *timep, struct tm *tmp)
+localtime_r(const time_t *restrict timep, struct tm *restrict tmp)
 {
   return localtime_tzset(timep, tmp);
 }
@@ -1695,8 +1697,8 @@
 */
 
 static struct tm *
-gmtsub(struct state const *sp, time_t const *timep, int_fast32_t offset,
-       struct tm *tmp)
+gmtsub(ATTRIBUTE_MAYBE_UNUSED struct state const *sp, time_t const *timep,
+       int_fast32_t offset, struct tm *tmp)
 {
 	register struct tm *	result;
 
@@ -1708,7 +1710,7 @@
 	** but this is no time for a treasure hunt.
 	*/
 	tmp->TM_ZONE = ((char *)
-			(offset ? wildabbr : gmtptr ? gmtptr->chars : gmt));
+			(offset ? wildabbr : gmtptr ? gmtptr->chars : utc));
 #endif /* defined TM_ZONE */
 	return result;
 }
@@ -1718,7 +1720,7 @@
 */
 
 struct tm *
-gmtime_r(const time_t *timep, struct tm *tmp)
+gmtime_r(time_t const *restrict timep, struct tm *restrict tmp)
 {
   gmtcheck();
   return gmtsub(gmtptr, timep, 0, tmp);
@@ -1727,19 +1729,26 @@
 struct tm *
 gmtime(const time_t *timep)
 {
+#if !SUPPORT_C89
+  static struct tm tm;
+#endif
   return gmtime_r(timep, &tm);
 }
 
-#ifdef STD_INSPIRED
+#if STD_INSPIRED
 
 struct tm *
 offtime(const time_t *timep, long offset)
 {
   gmtcheck();
+
+#if !SUPPORT_C89
+  static struct tm tm;
+#endif
   return gmtsub(gmtptr, timep, offset, &tm);
 }
 
-#endif /* defined STD_INSPIRED */
+#endif
 
 /*
 ** Return the number of leap years through the end of the given year
@@ -1825,6 +1834,12 @@
 		y = newy;
 	}
 
+#ifdef ckd_add
+	if (ckd_add(&tmp->tm_year, y, -TM_YEAR_BASE)) {
+	  errno = EOVERFLOW;
+	  return NULL;
+	}
+#else
 	if (!TYPE_SIGNED(time_t) && y < TM_YEAR_BASE) {
 	  int signed_y = y;
 	  tmp->tm_year = signed_y - TM_YEAR_BASE;
@@ -1835,6 +1850,7 @@
 	  errno = EOVERFLOW;
 	  return NULL;
 	}
+#endif
 	tmp->tm_yday = idays;
 	/*
 	** The "extra" mods below avoid overflow problems.
@@ -1868,27 +1884,6 @@
 	return tmp;
 }
 
-char *
-ctime(const time_t *timep)
-{
-/*
-** Section 4.12.3.2 of X3.159-1989 requires that
-**	The ctime function converts the calendar time pointed to by timer
-**	to local time in the form of a string. It is equivalent to
-**		asctime(localtime(timer))
-*/
-  struct tm *tmp = localtime(timep);
-  return tmp ? asctime(tmp) : NULL;
-}
-
-char *
-ctime_r(const time_t *timep, char *buf)
-{
-  struct tm mytm;
-  struct tm *tmp = localtime_r(timep, &mytm);
-  return tmp ? asctime_r(tmp, buf) : NULL;
-}
-
 /*
 ** Adapted from code provided by Robert Elz, who writes:
 **	The "best" way to do mktime I think is based on an idea of Bob
@@ -1899,7 +1894,7 @@
 */
 
 #ifndef WRONG
-#define WRONG	(-1)
+# define WRONG (-1)
 #endif /* !defined WRONG */
 
 /*
@@ -1909,6 +1904,9 @@
 static bool
 increment_overflow(int *ip, int j)
 {
+#ifdef ckd_add
+	return ckd_add(ip, *ip, j);
+#else
 	register int const	i = *ip;
 
 	/*
@@ -1921,22 +1919,30 @@
 		return true;
 	*ip += j;
 	return false;
+#endif
 }
 
 static bool
 increment_overflow32(int_fast32_t *const lp, int const m)
 {
+#ifdef ckd_add
+	return ckd_add(lp, *lp, m);
+#else
 	register int_fast32_t const	l = *lp;
 
 	if ((l >= 0) ? (m > INT_FAST32_MAX - l) : (m < INT_FAST32_MIN - l))
 		return true;
 	*lp += m;
 	return false;
+#endif
 }
 
 static bool
 increment_overflow_time(time_t *tp, int_fast32_t j)
 {
+#ifdef ckd_add
+	return ckd_add(tp, *tp, j);
+#else
 	/*
 	** This is like
 	** 'if (! (TIME_T_MIN <= *tp + j && *tp + j <= TIME_T_MAX)) ...',
@@ -1948,6 +1954,7 @@
 		return true;
 	*tp += j;
 	return false;
+#endif
 }
 
 static bool
@@ -1990,6 +1997,23 @@
 	return result;
 }
 
+/* Copy to *DEST from *SRC.  Copy only the members needed for mktime,
+   as other members might not be initialized.  */
+static void
+mktmcpy(struct tm *dest, struct tm const *src)
+{
+  dest->tm_sec = src->tm_sec;
+  dest->tm_min = src->tm_min;
+  dest->tm_hour = src->tm_hour;
+  dest->tm_mday = src->tm_mday;
+  dest->tm_mon = src->tm_mon;
+  dest->tm_year = src->tm_year;
+  dest->tm_isdst = src->tm_isdst;
+#if defined TM_GMTOFF && ! UNINIT_TRAP
+  dest->TM_GMTOFF = src->TM_GMTOFF;
+#endif
+}
+
 static time_t
 time2sub(struct tm *const tmp,
 	 struct tm *(*funcp)(struct state const *, time_t const *,
@@ -2011,7 +2035,8 @@
 	struct tm			yourtm, mytm;
 
 	*okayp = false;
-	yourtm = *tmp;
+	mktmcpy(&yourtm, tmp);
+
 	if (do_norm_secs) {
 		if (normalize_overflow(&yourtm.tm_min, &yourtm.tm_sec,
 			SECSPERMIN))
@@ -2053,14 +2078,19 @@
 				return WRONG;
 		}
 	}
+#ifdef ckd_add
+	if (ckd_add(&yourtm.tm_year, y, -TM_YEAR_BASE))
+	  return WRONG;
+#else
 	if (increment_overflow32(&y, -TM_YEAR_BASE))
 		return WRONG;
 	if (! (INT_MIN <= y && y <= INT_MAX))
 		return WRONG;
 	yourtm.tm_year = y;
+#endif
 	if (yourtm.tm_sec >= 0 && yourtm.tm_sec < SECSPERMIN)
 		saved_seconds = 0;
-	else if (y + TM_YEAR_BASE < EPOCH_YEAR) {
+	else if (yourtm.tm_year < EPOCH_YEAR - TM_YEAR_BASE) {
 		/*
 		** We can't set tm_sec to 0, because that might push the
 		** time below the minimum representable time.
@@ -2120,10 +2150,10 @@
 		    && (yourtm.TM_GMTOFF < 0
 			? (-SECSPERDAY <= yourtm.TM_GMTOFF
 			   && (mytm.TM_GMTOFF <=
-			       (SMALLEST(INT_FAST32_MAX, LONG_MAX)
+			       (min(INT_FAST32_MAX, LONG_MAX)
 				+ yourtm.TM_GMTOFF)))
 			: (yourtm.TM_GMTOFF <= SECSPERDAY
-			   && ((BIGGEST(INT_FAST32_MIN, LONG_MIN)
+			   && ((max(INT_FAST32_MIN, LONG_MIN)
 				+ yourtm.TM_GMTOFF)
 			       <= mytm.TM_GMTOFF)))) {
 		  /* MYTM matches YOURTM except with the wrong UT offset.
@@ -2294,7 +2324,7 @@
 #if NETBSD_INSPIRED
 
 time_t
-mktime_z(struct state *sp, struct tm *tmp)
+mktime_z(struct state *restrict sp, struct tm *restrict tmp)
 {
   return mktime_tzname(sp, tmp, false);
 }
@@ -2324,8 +2354,7 @@
   return t;
 }
 
-#ifdef STD_INSPIRED
-
+#if STD_INSPIRED
 time_t
 timelocal(struct tm *tmp)
 {
@@ -2333,13 +2362,9 @@
 		tmp->tm_isdst = -1;	/* in case it wasn't initialized */
 	return mktime(tmp);
 }
-
-time_t
-timegm(struct tm *tmp)
-{
-  return timeoff(tmp, 0);
-}
-
+#else
+static
+#endif
 time_t
 timeoff(struct tm *tmp, long offset)
 {
@@ -2349,7 +2374,18 @@
   return time1(tmp, gmtsub, gmtptr, offset);
 }
 
-#endif /* defined STD_INSPIRED */
+time_t
+timegm(struct tm *tmp)
+{
+  time_t t;
+  struct tm tmcpy;
+  mktmcpy(&tmcpy, tmp);
+  tmcpy.tm_wday = -1;
+  t = timeoff(&tmcpy, 0);
+  if (0 <= tmcpy.tm_wday)
+    *tmp = tmcpy;
+  return t;
+}
 
 static int_fast32_t
 leapcorr(struct state const *sp, time_t t)
@@ -2370,7 +2406,7 @@
 ** XXX--is the below the right way to conditionalize??
 */
 
-#ifdef STD_INSPIRED
+#if STD_INSPIRED
 
 /* NETBSD_INSPIRED_EXTERN functions are exported to callers if
    NETBSD_INSPIRED is defined, and are private otherwise.  */
@@ -2455,7 +2491,7 @@
   return t;
 }
 
-#endif /* defined STD_INSPIRED */
+#endif /* STD_INSPIRED */
 
 #if TZ_TIME_T
 
diff --git a/libc/tzcode/private.h b/libc/tzcode/private.h
index 4c03324..838ab2b 100644
--- a/libc/tzcode/private.h
+++ b/libc/tzcode/private.h
@@ -17,6 +17,36 @@
 ** Thank you!
 */
 
+/* PORT_TO_C89 means the code should work even if the underlying
+   compiler and library support only C89.  SUPPORT_C89 means the
+   tzcode library should support C89 callers in addition to the usual
+   support for C99-and-later callers.  These macros are obsolescent,
+   and the plan is to remove them along with any code needed only when
+   they are nonzero.  */
+#ifndef PORT_TO_C89
+# define PORT_TO_C89 0
+#endif
+#ifndef SUPPORT_C89
+# define SUPPORT_C89 0
+#endif
+
+#ifndef __STDC_VERSION__
+# define __STDC_VERSION__ 0
+#endif
+
+/* Define true, false and bool if they don't work out of the box.  */
+#if PORT_TO_C89 && __STDC_VERSION__ < 199901
+# define true 1
+# define false 0
+# define bool int
+#elif __STDC_VERSION__ < 202311
+# include <stdbool.h>
+#endif
+
+#if __STDC_VERSION__ < 202311
+# define static_assert(cond) extern int static_assert_check[(cond) ? 1 : -1]
+#endif
+
 /*
 ** zdump has been made independent of the rest of the time
 ** conversion package to increase confidence in the verification it provides.
@@ -36,79 +66,86 @@
 */
 
 #ifndef HAVE_DECL_ASCTIME_R
-#define HAVE_DECL_ASCTIME_R 1
+# define HAVE_DECL_ASCTIME_R 1
 #endif
 
-#if !defined HAVE_GENERIC && defined __has_extension
+#if !defined HAVE__GENERIC && defined __has_extension
 # if __has_extension(c_generic_selections)
-#  define HAVE_GENERIC 1
+#  define HAVE__GENERIC 1
 # else
-#  define HAVE_GENERIC 0
+#  define HAVE__GENERIC 0
 # endif
 #endif
 /* _Generic is buggy in pre-4.9 GCC.  */
-#if !defined HAVE_GENERIC && defined __GNUC__
-# define HAVE_GENERIC (4 < __GNUC__ + (9 <= __GNUC_MINOR__))
+#if !defined HAVE__GENERIC && defined __GNUC__ && !defined __STRICT_ANSI__
+# define HAVE__GENERIC (4 < __GNUC__ + (9 <= __GNUC_MINOR__))
 #endif
-#ifndef HAVE_GENERIC
-# define HAVE_GENERIC (201112 <= __STDC_VERSION__)
+#ifndef HAVE__GENERIC
+# define HAVE__GENERIC (201112 <= __STDC_VERSION__)
 #endif
 
+#if !defined HAVE_GETTEXT && defined __has_include
+# if __has_include(<libintl.h>)
+#  define HAVE_GETTEXT true
+# endif
+#endif
 #ifndef HAVE_GETTEXT
-#define HAVE_GETTEXT		0
-#endif /* !defined HAVE_GETTEXT */
+# define HAVE_GETTEXT false
+#endif
 
 #ifndef HAVE_INCOMPATIBLE_CTIME_R
-#define HAVE_INCOMPATIBLE_CTIME_R	0
+# define HAVE_INCOMPATIBLE_CTIME_R 0
 #endif
 
 #ifndef HAVE_LINK
-#define HAVE_LINK		1
+# define HAVE_LINK 1
 #endif /* !defined HAVE_LINK */
 
 #ifndef HAVE_MALLOC_ERRNO
-#define HAVE_MALLOC_ERRNO 1
+# define HAVE_MALLOC_ERRNO 1
 #endif
 
 #ifndef HAVE_POSIX_DECLS
-#define HAVE_POSIX_DECLS 1
+# define HAVE_POSIX_DECLS 1
 #endif
 
-#ifndef HAVE_STDBOOL_H
-#define HAVE_STDBOOL_H (199901 <= __STDC_VERSION__)
+#ifndef HAVE_SETENV
+# define HAVE_SETENV 1
 #endif
 
 #ifndef HAVE_STRDUP
-#define HAVE_STRDUP 1
-#endif
-
-#ifndef HAVE_STRTOLL
-#define HAVE_STRTOLL 1
+# define HAVE_STRDUP 1
 #endif
 
 #ifndef HAVE_SYMLINK
-#define HAVE_SYMLINK		1
+# define HAVE_SYMLINK 1
 #endif /* !defined HAVE_SYMLINK */
 
+#if !defined HAVE_SYS_STAT_H && defined __has_include
+# if !__has_include(<sys/stat.h>)
+#  define HAVE_SYS_STAT_H false
+# endif
+#endif
 #ifndef HAVE_SYS_STAT_H
-#define HAVE_SYS_STAT_H		1
-#endif /* !defined HAVE_SYS_STAT_H */
+# define HAVE_SYS_STAT_H true
+#endif
 
+#if !defined HAVE_UNISTD_H && defined __has_include
+# if !__has_include(<unistd.h>)
+#  define HAVE_UNISTD_H false
+# endif
+#endif
 #ifndef HAVE_UNISTD_H
-#define HAVE_UNISTD_H		1
-#endif /* !defined HAVE_UNISTD_H */
-
-#ifndef HAVE_UTMPX_H
-#define HAVE_UTMPX_H		1
-#endif /* !defined HAVE_UTMPX_H */
+# define HAVE_UNISTD_H true
+#endif
 
 #ifndef NETBSD_INSPIRED
 # define NETBSD_INSPIRED 1
 #endif
 
 #if HAVE_INCOMPATIBLE_CTIME_R
-#define asctime_r _incompatible_asctime_r
-#define ctime_r _incompatible_ctime_r
+# define asctime_r _incompatible_asctime_r
+# define ctime_r _incompatible_ctime_r
 #endif /* HAVE_INCOMPATIBLE_CTIME_R */
 
 /* Enable tm_gmtoff, tm_zone, and environ on GNUish systems.  */
@@ -118,15 +155,17 @@
 /* Enable strtoimax on pre-C99 Solaris 11.  */
 #define __EXTENSIONS__ 1
 
-/* To avoid having 'stat' fail unnecessarily with errno == EOVERFLOW,
-   enable large files on GNUish systems ...  */
+/* On GNUish systems where time_t might be 32 or 64 bits, use 64.
+   On these platforms _FILE_OFFSET_BITS must also be 64; otherwise
+   setting _TIME_BITS to 64 does not work.  The code does not
+   otherwise rely on _FILE_OFFSET_BITS being 64, since it does not
+   use off_t or functions like 'stat' that depend on off_t.  */
 #ifndef _FILE_OFFSET_BITS
 # define _FILE_OFFSET_BITS 64
 #endif
-/* ... and on AIX ...  */
-#define _LARGE_FILES 1
-/* ... and enable large inode numbers on Mac OS X 10.5 and later.  */
-#define _DARWIN_USE_64_BIT_INODE 1
+#if !defined _TIME_BITS && _FILE_OFFSET_BITS == 64
+# define _TIME_BITS 64
+#endif
 
 /*
 ** Nested includes
@@ -157,8 +196,11 @@
 #undef tzalloc
 #undef tzfree
 
-#include <sys/types.h>	/* for time_t */
+#include <stddef.h>
 #include <string.h>
+#if !PORT_TO_C89
+# include <inttypes.h>
+#endif
 #include <limits.h>	/* for CHAR_BIT et al. */
 #include <stdlib.h>
 
@@ -168,6 +210,9 @@
 # define EINVAL ERANGE
 #endif
 
+#ifndef ELOOP
+# define ELOOP EINVAL
+#endif
 #ifndef ENAMETOOLONG
 # define ENAMETOOLONG EINVAL
 #endif
@@ -182,11 +227,11 @@
 #endif
 
 #if HAVE_GETTEXT
-#include <libintl.h>
+# include <libintl.h>
 #endif /* HAVE_GETTEXT */
 
 #if HAVE_UNISTD_H
-#include <unistd.h>	/* for R_OK, and other POSIX goodness */
+# include <unistd.h> /* for R_OK, and other POSIX goodness */
 #endif /* HAVE_UNISTD_H */
 
 #ifndef HAVE_STRFTIME_L
@@ -222,24 +267,29 @@
 #endif
 
 #ifndef R_OK
-#define R_OK	4
+# define R_OK 4
 #endif /* !defined R_OK */
 
+#if PORT_TO_C89
+
 /*
 ** Define HAVE_STDINT_H's default value here, rather than at the
 ** start, since __GLIBC__ and INTMAX_MAX's values depend on
-** previously-included files.  glibc 2.1 and Solaris 10 and later have
+** previously included files.  glibc 2.1 and Solaris 10 and later have
 ** stdint.h, even with pre-C99 compilers.
 */
+#if !defined HAVE_STDINT_H && defined __has_include
+# define HAVE_STDINT_H true /* C23 __has_include implies C99 stdint.h.  */
+#endif
 #ifndef HAVE_STDINT_H
-#define HAVE_STDINT_H \
+# define HAVE_STDINT_H \
    (199901 <= __STDC_VERSION__ \
-    || 2 < __GLIBC__ + (1 <= __GLIBC_MINOR__)	\
+    || 2 < __GLIBC__ + (1 <= __GLIBC_MINOR__) \
     || __CYGWIN__ || INTMAX_MAX)
 #endif /* !defined HAVE_STDINT_H */
 
 #if HAVE_STDINT_H
-#include <stdint.h>
+# include <stdint.h>
 #endif /* !HAVE_STDINT_H */
 
 #ifndef HAVE_INTTYPES_H
@@ -250,36 +300,36 @@
 #endif
 
 /* Pre-C99 GCC compilers define __LONG_LONG_MAX__ instead of LLONG_MAX.  */
-#ifdef __LONG_LONG_MAX__
+#if defined __LONG_LONG_MAX__ && !defined __STRICT_ANSI__
 # ifndef LLONG_MAX
 #  define LLONG_MAX __LONG_LONG_MAX__
 # endif
 # ifndef LLONG_MIN
 #  define LLONG_MIN (-1 - LLONG_MAX)
 # endif
+# ifndef ULLONG_MAX
+#  define ULLONG_MAX (LLONG_MAX * 2ull + 1)
+# endif
 #endif
 
 #ifndef INT_FAST64_MAX
-# ifdef LLONG_MAX
-typedef long long	int_fast64_t;
-#  define INT_FAST64_MIN LLONG_MIN
-#  define INT_FAST64_MAX LLONG_MAX
-# else
-#  if LONG_MAX >> 31 < 0xffffffff
-Please use a compiler that supports a 64-bit integer type (or wider);
-you may need to compile with "-DHAVE_STDINT_H".
-#  endif
-typedef long		int_fast64_t;
+# if 1 <= LONG_MAX >> 31 >> 31
+typedef long int_fast64_t;
 #  define INT_FAST64_MIN LONG_MIN
 #  define INT_FAST64_MAX LONG_MAX
+# else
+/* If this fails, compile with -DHAVE_STDINT_H or with a better compiler.  */
+typedef long long int_fast64_t;
+#  define INT_FAST64_MIN LLONG_MIN
+#  define INT_FAST64_MAX LLONG_MAX
 # endif
 #endif
 
 #ifndef PRIdFAST64
-# if INT_FAST64_MAX == LLONG_MAX
-#  define PRIdFAST64 "lld"
-# else
+# if INT_FAST64_MAX == LONG_MAX
 #  define PRIdFAST64 "ld"
+# else
+#  define PRIdFAST64 "lld"
 # endif
 #endif
 
@@ -302,6 +352,9 @@
 #ifndef INTMAX_MAX
 # ifdef LLONG_MAX
 typedef long long intmax_t;
+#  ifndef HAVE_STRTOLL
+#   define HAVE_STRTOLL true
+#  endif
 #  if HAVE_STRTOLL
 #   define strtoimax strtoll
 #  endif
@@ -325,70 +378,183 @@
 # endif
 #endif
 
+#ifndef PTRDIFF_MAX
+# define PTRDIFF_MAX MAXVAL(ptrdiff_t, TYPE_BIT(ptrdiff_t))
+#endif
+
 #ifndef UINT_FAST32_MAX
 typedef unsigned long uint_fast32_t;
 #endif
 
 #ifndef UINT_FAST64_MAX
-# if defined ULLONG_MAX || defined __LONG_LONG_MAX__
-typedef unsigned long long uint_fast64_t;
+# if 3 <= ULONG_MAX >> 31 >> 31
+typedef unsigned long uint_fast64_t;
+#  define UINT_FAST64_MAX ULONG_MAX
 # else
-#  if ULONG_MAX >> 31 >> 1 < 0xffffffff
-Please use a compiler that supports a 64-bit integer type (or wider);
-you may need to compile with "-DHAVE_STDINT_H".
-#  endif
-typedef unsigned long	uint_fast64_t;
+/* If this fails, compile with -DHAVE_STDINT_H or with a better compiler.  */
+typedef unsigned long long uint_fast64_t;
+#  define UINT_FAST64_MAX ULLONG_MAX
 # endif
 #endif
 
 #ifndef UINTMAX_MAX
-# if defined ULLONG_MAX || defined __LONG_LONG_MAX__
+# ifdef ULLONG_MAX
 typedef unsigned long long uintmax_t;
+#  define UINTMAX_MAX ULLONG_MAX
 # else
 typedef unsigned long uintmax_t;
+#  define UINTMAX_MAX ULONG_MAX
 # endif
 #endif
 
 #ifndef PRIuMAX
-# if defined ULLONG_MAX || defined __LONG_LONG_MAX__
+# ifdef ULLONG_MAX
 #  define PRIuMAX "llu"
 # else
 #  define PRIuMAX "lu"
 # endif
 #endif
 
-#ifndef INT32_MAX
-#define INT32_MAX 0x7fffffff
-#endif /* !defined INT32_MAX */
-#ifndef INT32_MIN
-#define INT32_MIN (-1 - INT32_MAX)
-#endif /* !defined INT32_MIN */
-
 #ifndef SIZE_MAX
-#define SIZE_MAX ((size_t) -1)
+# define SIZE_MAX ((size_t) -1)
+#endif
+
+#endif /* PORT_TO_C89 */
+
+/* The maximum size of any created object, as a signed integer.
+   Although the C standard does not outright prohibit larger objects,
+   behavior is undefined if the result of pointer subtraction does not
+   fit into ptrdiff_t, and the code assumes in several places that
+   pointer subtraction works.  As a practical matter it's OK to not
+   support objects larger than this.  */
+#define INDEX_MAX ((ptrdiff_t) min(PTRDIFF_MAX, SIZE_MAX))
+
+/* Support ckd_add, ckd_sub, ckd_mul on C23 or recent-enough GCC-like
+   hosts, unless compiled with -DHAVE_STDCKDINT_H=0 or with pre-C23 EDG.  */
+#if !defined HAVE_STDCKDINT_H && defined __has_include
+# if __has_include(<stdckdint.h>)
+#  define HAVE_STDCKDINT_H true
+# endif
+#endif
+#ifdef HAVE_STDCKDINT_H
+# if HAVE_STDCKDINT_H
+#  include <stdckdint.h>
+# endif
+#elif defined __EDG__
+/* Do nothing, to work around EDG bug <https://bugs.gnu.org/53256>.  */
+#elif defined __has_builtin
+# if __has_builtin(__builtin_add_overflow)
+#  define ckd_add(r, a, b) __builtin_add_overflow(a, b, r)
+# endif
+# if __has_builtin(__builtin_sub_overflow)
+#  define ckd_sub(r, a, b) __builtin_sub_overflow(a, b, r)
+# endif
+# if __has_builtin(__builtin_mul_overflow)
+#  define ckd_mul(r, a, b) __builtin_mul_overflow(a, b, r)
+# endif
+#elif 7 <= __GNUC__
+# define ckd_add(r, a, b) __builtin_add_overflow(a, b, r)
+# define ckd_sub(r, a, b) __builtin_sub_overflow(a, b, r)
+# define ckd_mul(r, a, b) __builtin_mul_overflow(a, b, r)
 #endif
 
 #if 3 <= __GNUC__
-# define ATTRIBUTE_CONST __attribute__((const))
-# define ATTRIBUTE_MALLOC __attribute__((__malloc__))
-# define ATTRIBUTE_PURE __attribute__((__pure__))
-# define ATTRIBUTE_FORMAT(spec) __attribute__((__format__ spec))
+# define ATTRIBUTE_MALLOC __attribute__((malloc))
+# define ATTRIBUTE_FORMAT(spec) __attribute__((format spec))
 #else
-# define ATTRIBUTE_CONST /* empty */
 # define ATTRIBUTE_MALLOC /* empty */
-# define ATTRIBUTE_PURE /* empty */
 # define ATTRIBUTE_FORMAT(spec) /* empty */
 #endif
 
-#if !defined _Noreturn && __STDC_VERSION__ < 201112
-# if 2 < __GNUC__ + (8 <= __GNUC_MINOR__)
-#  define _Noreturn __attribute__((__noreturn__))
+#if (defined __has_c_attribute \
+     && (202311 <= __STDC_VERSION__ || !defined __STRICT_ANSI__))
+# define HAVE___HAS_C_ATTRIBUTE true
+#else
+# define HAVE___HAS_C_ATTRIBUTE false
+#endif
+
+#if HAVE___HAS_C_ATTRIBUTE
+# if __has_c_attribute(deprecated)
+#  define ATTRIBUTE_DEPRECATED [[deprecated]]
+# endif
+#endif
+#ifndef ATTRIBUTE_DEPRECATED
+# if 3 < __GNUC__ + (2 <= __GNUC_MINOR__)
+#  define ATTRIBUTE_DEPRECATED __attribute__((deprecated))
 # else
-#  define _Noreturn
+#  define ATTRIBUTE_DEPRECATED /* empty */
 # endif
 #endif
 
-#if __STDC_VERSION__ < 199901 && !defined restrict
+#if HAVE___HAS_C_ATTRIBUTE
+# if __has_c_attribute(fallthrough)
+#  define ATTRIBUTE_FALLTHROUGH [[fallthrough]]
+# endif
+#endif
+#ifndef ATTRIBUTE_FALLTHROUGH
+# if 7 <= __GNUC__
+#  define ATTRIBUTE_FALLTHROUGH __attribute__((fallthrough))
+# else
+#  define ATTRIBUTE_FALLTHROUGH ((void) 0)
+# endif
+#endif
+
+#if HAVE___HAS_C_ATTRIBUTE
+# if __has_c_attribute(maybe_unused)
+#  define ATTRIBUTE_MAYBE_UNUSED [[maybe_unused]]
+# endif
+#endif
+#ifndef ATTRIBUTE_MAYBE_UNUSED
+# if 2 < __GNUC__ + (7 <= __GNUC_MINOR__)
+#  define ATTRIBUTE_MAYBE_UNUSED __attribute__((unused))
+# else
+#  define ATTRIBUTE_MAYBE_UNUSED /* empty */
+# endif
+#endif
+
+#if HAVE___HAS_C_ATTRIBUTE
+# if __has_c_attribute(noreturn)
+#  define ATTRIBUTE_NORETURN [[noreturn]]
+# endif
+#endif
+#ifndef ATTRIBUTE_NORETURN
+# if 201112 <= __STDC_VERSION__
+#  define ATTRIBUTE_NORETURN _Noreturn
+# elif 2 < __GNUC__ + (8 <= __GNUC_MINOR__)
+#  define ATTRIBUTE_NORETURN __attribute__((noreturn))
+# else
+#  define ATTRIBUTE_NORETURN /* empty */
+# endif
+#endif
+
+#if HAVE___HAS_C_ATTRIBUTE
+# if __has_c_attribute(reproducible)
+#  define ATTRIBUTE_REPRODUCIBLE [[reproducible]]
+# endif
+#endif
+#ifndef ATTRIBUTE_REPRODUCIBLE
+# if 3 <= __GNUC__
+#  define ATTRIBUTE_REPRODUCIBLE __attribute__((pure))
+# else
+#  define ATTRIBUTE_REPRODUCIBLE /* empty */
+# endif
+#endif
+
+#if HAVE___HAS_C_ATTRIBUTE
+# if __has_c_attribute(unsequenced)
+#  define ATTRIBUTE_UNSEQUENCED [[unsequenced]]
+# endif
+#endif
+#ifndef ATTRIBUTE_UNSEQUENCED
+# if 3 <= __GNUC__
+#  define ATTRIBUTE_UNSEQUENCED __attribute__((const))
+# else
+#  define ATTRIBUTE_UNSEQUENCED /* empty */
+# endif
+#endif
+
+#if (__STDC_VERSION__ < 199901 && !defined restrict \
+     && (PORT_TO_C89 || defined _MSC_VER))
 # define restrict /* empty */
 #endif
 
@@ -505,11 +671,16 @@
 #  define altzone tz_altzone
 # endif
 
-char *asctime(struct tm const *);
+# if __STDC_VERSION__ < 202311
+#  define DEPRECATED_IN_C23 /* empty */
+# else
+#  define DEPRECATED_IN_C23 ATTRIBUTE_DEPRECATED
+# endif
+DEPRECATED_IN_C23 char *asctime(struct tm const *);
 char *asctime_r(struct tm const *restrict, char *restrict);
-char *ctime(time_t const *);
+DEPRECATED_IN_C23 char *ctime(time_t const *);
 char *ctime_r(time_t const *, char *);
-double difftime(time_t, time_t) ATTRIBUTE_CONST;
+ATTRIBUTE_UNSEQUENCED double difftime(time_t, time_t);
 size_t strftime(char *restrict, size_t, char const *restrict,
 		struct tm const *restrict);
 # if HAVE_STRFTIME_L
@@ -522,9 +693,24 @@
 struct tm *localtime_r(time_t const *restrict, struct tm *restrict);
 time_t mktime(struct tm *);
 time_t time(time_t *);
+time_t timegm(struct tm *);
 void tzset(void);
 #endif
 
+#ifndef HAVE_DECL_TIMEGM
+# if (202311 <= __STDC_VERSION__ \
+      || defined __GLIBC__ || defined __tm_zone /* musl */ \
+      || defined __FreeBSD__ || defined __NetBSD__ || defined __OpenBSD__ \
+      || (defined __APPLE__ && defined __MACH__))
+#  define HAVE_DECL_TIMEGM true
+# else
+#  define HAVE_DECL_TIMEGM false
+# endif
+#endif
+#if !HAVE_DECL_TIMEGM && !defined timegm
+time_t timegm(struct tm *);
+#endif
+
 #if !HAVE_DECL_ASCTIME_R && !defined asctime_r
 extern char *asctime_r(struct tm const *restrict, char *restrict);
 #endif
@@ -557,13 +743,13 @@
 ** declarations if time_tz is defined.
 */
 
-#ifdef STD_INSPIRED
+#ifndef STD_INSPIRED
+# define STD_INSPIRED 0
+#endif
+#if STD_INSPIRED
 # if TZ_TIME_T || !defined offtime
 struct tm *offtime(time_t const *, long);
 # endif
-# if TZ_TIME_T || !defined timegm
-time_t timegm(struct tm *);
-# endif
 # if TZ_TIME_T || !defined timelocal
 time_t timelocal(struct tm *);
 # endif
@@ -581,6 +767,7 @@
 /* Infer TM_ZONE on systems where this information is known, but suppress
    guessing if NO_TM_ZONE is defined.  Similarly for TM_GMTOFF.  */
 #if (defined __GLIBC__ \
+     || defined __tm_zone /* musl */ \
      || defined __FreeBSD__ || defined __NetBSD__ || defined __OpenBSD__ \
      || (defined __APPLE__ && defined __MACH__))
 # if !defined TM_GMTOFF && !defined NO_TM_GMTOFF
@@ -606,12 +793,12 @@
 time_t mktime_z(timezone_t restrict, struct tm *restrict);
 timezone_t tzalloc(char const *);
 void tzfree(timezone_t);
-# ifdef STD_INSPIRED
+# if STD_INSPIRED
 #  if TZ_TIME_T || !defined posix2time_z
-time_t posix2time_z(timezone_t, time_t) ATTRIBUTE_PURE;
+ATTRIBUTE_REPRODUCIBLE time_t posix2time_z(timezone_t, time_t);
 #  endif
 #  if TZ_TIME_T || !defined time2posix_z
-time_t time2posix_z(timezone_t, time_t) ATTRIBUTE_PURE;
+ATTRIBUTE_REPRODUCIBLE time_t time2posix_z(timezone_t, time_t);
 #  endif
 # endif
 #endif
@@ -620,18 +807,15 @@
 ** Finally, some convenience items.
 */
 
-#if HAVE_STDBOOL_H
-# include <stdbool.h>
-#else
-# define true 1
-# define false 0
-# define bool int
-#endif
-
-#define TYPE_BIT(type)	(sizeof(type) * CHAR_BIT)
+#define TYPE_BIT(type) (CHAR_BIT * (ptrdiff_t) sizeof(type))
 #define TYPE_SIGNED(type) (((type) -1) < 0)
 #define TWOS_COMPLEMENT(t) ((t) ~ (t) 0 < 0)
 
+/* Minimum and maximum of two values.  Use lower case to avoid
+   naming clashes with standard include files.  */
+#define max(a, b) ((a) > (b) ? (a) : (b))
+#define min(a, b) ((a) < (b) ? (a) : (b))
+
 /* Max and min values of the integer type T, of which only the bottom
    B bits are used, and where the highest-order used bit is considered
    to be a sign bit if T is signed.  */
@@ -651,7 +835,7 @@
    This implementation assumes no padding if time_t is signed and
    either the compiler lacks support for _Generic or time_t is not one
    of the standard signed integer types.  */
-#if HAVE_GENERIC
+#if HAVE__GENERIC
 # define TIME_T_MIN \
     _Generic((time_t) 0, \
 	     signed char: SCHAR_MIN, short: SHRT_MIN, \
@@ -664,10 +848,23 @@
 		int: INT_MAX, long: LONG_MAX, long long: LLONG_MAX, \
 		default: TIME_T_MAX_NO_PADDING)			    \
      : (time_t) -1)
+enum { SIGNED_PADDING_CHECK_NEEDED
+         = _Generic((time_t) 0,
+		    signed char: false, short: false,
+		    int: false, long: false, long long: false,
+		    default: true) };
 #else
 # define TIME_T_MIN TIME_T_MIN_NO_PADDING
 # define TIME_T_MAX TIME_T_MAX_NO_PADDING
+enum { SIGNED_PADDING_CHECK_NEEDED = true };
 #endif
+/* Try to check the padding assumptions.  Although TIME_T_MAX and the
+   following check can both have undefined behavior on oddball
+   platforms due to shifts exceeding widths of signed integers, these
+   platforms' compilers are likely to diagnose these issues in integer
+   constant expressions, so it shouldn't hurt to check statically.  */
+static_assert(! TYPE_SIGNED(time_t) || ! SIGNED_PADDING_CHECK_NEEDED
+	      || TIME_T_MAX >> (TYPE_BIT(time_t) - 2) == 1);
 
 /*
 ** 302 / 1000 is log10(2.0) rounded up.
@@ -689,21 +886,30 @@
 # define INITIALIZE(x)
 #endif
 
+/* Whether memory access must strictly follow the C standard.
+   If 0, it's OK to read uninitialized storage so long as the value is
+   not relied upon.  Defining it to 0 lets mktime access parts of
+   struct tm that might be uninitialized, as a heuristic when the
+   standard doesn't say what to return and when tm_gmtoff can help
+   mktime likely infer a better value.  */
 #ifndef UNINIT_TRAP
 # define UNINIT_TRAP 0
 #endif
 
 #ifdef DEBUG
-# define UNREACHABLE() abort()
-#elif 4 < __GNUC__ + (5 <= __GNUC_MINOR__)
-# define UNREACHABLE() __builtin_unreachable()
-#elif defined __has_builtin
-# if __has_builtin(__builtin_unreachable)
-#  define UNREACHABLE() __builtin_unreachable()
+# undef unreachable
+# define unreachable() abort()
+#elif !defined unreachable
+# ifdef __has_builtin
+#  if __has_builtin(__builtin_unreachable)
+#   define unreachable() __builtin_unreachable()
+#  endif
+# elif 4 < __GNUC__ + (5 <= __GNUC_MINOR__)
+#  define unreachable() __builtin_unreachable()
 # endif
-#endif
-#ifndef UNREACHABLE
-# define UNREACHABLE() ((void) 0)
+# ifndef unreachable
+#  define unreachable() ((void) 0)
+# endif
 #endif
 
 /*
@@ -725,53 +931,61 @@
 #if HAVE_INCOMPATIBLE_CTIME_R
 #undef asctime_r
 #undef ctime_r
-char *asctime_r(struct tm const *, char *);
+char *asctime_r(struct tm const *restrict, char *restrict);
 char *ctime_r(time_t const *, char *);
 #endif /* HAVE_INCOMPATIBLE_CTIME_R */
 
 /* Handy macros that are independent of tzfile implementation.  */
 
-#define SECSPERMIN	60
-#define MINSPERHOUR	60
-#define HOURSPERDAY	24
-#define DAYSPERWEEK	7
-#define DAYSPERNYEAR	365
-#define DAYSPERLYEAR	366
-#define SECSPERHOUR	(SECSPERMIN * MINSPERHOUR)
-#define SECSPERDAY	((int_fast32_t) SECSPERHOUR * HOURSPERDAY)
-#define MONSPERYEAR	12
+enum {
+  SECSPERMIN = 60,
+  MINSPERHOUR = 60,
+  SECSPERHOUR = SECSPERMIN * MINSPERHOUR,
+  HOURSPERDAY = 24,
+  DAYSPERWEEK = 7,
+  DAYSPERNYEAR = 365,
+  DAYSPERLYEAR = DAYSPERNYEAR + 1,
+  MONSPERYEAR = 12,
+  YEARSPERREPEAT = 400	/* years before a Gregorian repeat */
+};
 
-#define YEARSPERREPEAT		400	/* years before a Gregorian repeat */
+#define SECSPERDAY	((int_fast32_t) SECSPERHOUR * HOURSPERDAY)
+
 #define DAYSPERREPEAT		((int_fast32_t) 400 * 365 + 100 - 4 + 1)
 #define SECSPERREPEAT		((int_fast64_t) DAYSPERREPEAT * SECSPERDAY)
 #define AVGSECSPERYEAR		(SECSPERREPEAT / YEARSPERREPEAT)
 
-#define TM_SUNDAY	0
-#define TM_MONDAY	1
-#define TM_TUESDAY	2
-#define TM_WEDNESDAY	3
-#define TM_THURSDAY	4
-#define TM_FRIDAY	5
-#define TM_SATURDAY	6
+enum {
+  TM_SUNDAY,
+  TM_MONDAY,
+  TM_TUESDAY,
+  TM_WEDNESDAY,
+  TM_THURSDAY,
+  TM_FRIDAY,
+  TM_SATURDAY
+};
 
-#define TM_JANUARY	0
-#define TM_FEBRUARY	1
-#define TM_MARCH	2
-#define TM_APRIL	3
-#define TM_MAY		4
-#define TM_JUNE		5
-#define TM_JULY		6
-#define TM_AUGUST	7
-#define TM_SEPTEMBER	8
-#define TM_OCTOBER	9
-#define TM_NOVEMBER	10
-#define TM_DECEMBER	11
+enum {
+  TM_JANUARY,
+  TM_FEBRUARY,
+  TM_MARCH,
+  TM_APRIL,
+  TM_MAY,
+  TM_JUNE,
+  TM_JULY,
+  TM_AUGUST,
+  TM_SEPTEMBER,
+  TM_OCTOBER,
+  TM_NOVEMBER,
+  TM_DECEMBER
+};
 
-#define TM_YEAR_BASE	1900
-#define TM_WDAY_BASE	TM_MONDAY
-
-#define EPOCH_YEAR	1970
-#define EPOCH_WDAY	TM_THURSDAY
+enum {
+  TM_YEAR_BASE = 1900,
+  TM_WDAY_BASE = TM_MONDAY,
+  EPOCH_YEAR = 1970,
+  EPOCH_WDAY = TM_THURSDAY
+};
 
 #define isleap(y) (((y) % 4) == 0 && (((y) % 100) != 0 || ((y) % 400) == 0))
 
diff --git a/libc/tzcode/strftime.c b/libc/tzcode/strftime.c
index d04c5ba..4cde556 100644
--- a/libc/tzcode/strftime.c
+++ b/libc/tzcode/strftime.c
@@ -71,8 +71,6 @@
     const char *    date_fmt;
 };
 
-#define Locale  (&C_time_locale)
-
 static const struct lc_time_T   C_time_locale = {
     {
         "Jan", "Feb", "Mar", "Apr", "May", "Jun",
@@ -128,13 +126,14 @@
 static char *   _yconv(int, int, bool, bool, char *, const char *, int);
 
 #ifndef YEAR_2000_NAME
-#define YEAR_2000_NAME  "CHECK_STRFTIME_FORMATS_FOR_TWO_DIGIT_YEARS"
+# define YEAR_2000_NAME  "CHECK_STRFTIME_FORMATS_FOR_TWO_DIGIT_YEARS"
 #endif /* !defined YEAR_2000_NAME */
 
 #if HAVE_STRFTIME_L
 size_t
-strftime_l(char *s, size_t maxsize, char const *format, struct tm const *t,
-	   locale_t locale)
+strftime_l(char *restrict s, size_t maxsize, char const *restrict format,
+	   struct tm const *restrict t,
+	   ATTRIBUTE_MAYBE_UNUSED locale_t locale)
 {
   /* Just call strftime, as only the C locale is supported.  */
   return strftime(s, maxsize, format, t);
@@ -144,7 +143,8 @@
 #define FORCE_LOWER_CASE 0x100 /* Android extension. */
 
 size_t
-strftime(char *s, size_t maxsize, const char *format, const struct tm *t)
+strftime(char *restrict s, size_t maxsize, char const *restrict format,
+	 struct tm const *restrict t)
 {
     char *  p;
     int saved_errno = errno;
@@ -217,6 +217,8 @@
 _fmt(const char *format, const struct tm *t, char *pt,
         const char *ptlim, enum warn *warnp)
 {
+	struct lc_time_T const *Locale = &C_time_locale;
+
     for ( ; *format; ++format) {
         if (*format == '%') {
             int modifier = 0;
@@ -378,12 +380,21 @@
                     char buf[INT_STRLEN_MAXIMUM(time64_t) + 1] __attribute__((__uninitialized__));
                     time64_t    mkt;
 
-                    tm = *t;
+          					tm.tm_sec = t->tm_sec;
+					          tm.tm_min = t->tm_min;
+          					tm.tm_hour = t->tm_hour;
+					          tm.tm_mday = t->tm_mday;
+          					tm.tm_mon = t->tm_mon;
+					          tm.tm_year = t->tm_year;
+          					tm.tm_isdst = t->tm_isdst;
+#if defined TM_GMTOFF && ! UNINIT_TRAP
+					          tm.TM_GMTOFF = t->TM_GMTOFF;
+#endif
                     mkt = mktime64(&tm);
-					/* There is no portable, definitive
-					   test for whether whether mktime
-					   succeeded, so treat (time_t) -1 as
-					   the success that it might be.  */
+					/* If mktime fails, %s expands to the
+              value of (time_t) -1 as a failure
+              marker; this is better in practice
+              than strftime failing.  */
                     if (TYPE_SIGNED(time64_t)) {
                       intmax_t n = mkt;
                       sprintf(buf, "%"PRIdMAX, n);
@@ -607,19 +618,19 @@
 # endif
                 negative = diff < 0;
                 if (diff == 0) {
-#ifdef TM_ZONE
+# ifdef TM_ZONE
                   // Android-changed: do not use TM_ZONE as it is as it may be null.
                   {
                     const char* zone = _safe_tm_zone(t);
                     negative = zone[0] == '-';
                   }
-#else
+# else
                     negative = t->tm_isdst < 0;
-# if HAVE_TZNAME
+#  if HAVE_TZNAME
                     if (tzname[t->tm_isdst != 0][0] == '-')
                         negative = true;
+#  endif
 # endif
-#endif
                 }
                 if (negative) {
                     sign = "-";
@@ -748,7 +759,7 @@
     register int    lead;
     register int    trail;
 
-#define DIVISOR 100
+    int DIVISOR = 100;
     trail = a % DIVISOR + b % DIVISOR;
     lead = a / DIVISOR + b / DIVISOR + trail / DIVISOR;
     trail %= DIVISOR;
diff --git a/libc/tzcode/tzfile.h b/libc/tzcode/tzfile.h
index c5f9967..7ac8b51 100644
--- a/libc/tzcode/tzfile.h
+++ b/libc/tzcode/tzfile.h
@@ -22,15 +22,15 @@
 */
 
 #ifndef TZDIR
-#define TZDIR	"/usr/share/zoneinfo" /* Time zone object file directory */
+# define TZDIR "/usr/share/zoneinfo" /* Time zone object file directory */
 #endif /* !defined TZDIR */
 
 #ifndef TZDEFAULT
-#define TZDEFAULT	"/etc/localtime"
+# define TZDEFAULT "/etc/localtime"
 #endif /* !defined TZDEFAULT */
 
 #ifndef TZDEFRULES
-#define TZDEFRULES	"posixrules"
+# define TZDEFRULES "posixrules"
 #endif /* !defined TZDEFRULES */
 
 
@@ -103,21 +103,25 @@
 */
 
 #ifndef TZ_MAX_TIMES
-#define TZ_MAX_TIMES	2000
+/* This must be at least 242 for Europe/London with 'zic -b fat'.  */
+# define TZ_MAX_TIMES 2000
 #endif /* !defined TZ_MAX_TIMES */
 
 #ifndef TZ_MAX_TYPES
-/* This must be at least 17 for Europe/Samara and Europe/Vilnius.  */
-#define TZ_MAX_TYPES	256 /* Limited by what (unsigned char)'s can hold */
+/* This must be at least 18 for Europe/Vilnius with 'zic -b fat'.  */
+# define TZ_MAX_TYPES 256 /* Limited by what (unsigned char)'s can hold */
 #endif /* !defined TZ_MAX_TYPES */
 
 #ifndef TZ_MAX_CHARS
-#define TZ_MAX_CHARS	50	/* Maximum number of abbreviation characters */
+/* This must be at least 40 for America/Anchorage.  */
+# define TZ_MAX_CHARS 50	/* Maximum number of abbreviation characters */
 				/* (limited by what unsigned chars can hold) */
 #endif /* !defined TZ_MAX_CHARS */
 
 #ifndef TZ_MAX_LEAPS
-#define TZ_MAX_LEAPS	50	/* Maximum number of leap second corrections */
+/* This must be at least 27 for leap seconds from 1972 through mid-2023.
+   There's a plan to discontinue leap seconds by 2035.  */
+# define TZ_MAX_LEAPS 50	/* Maximum number of leap second corrections */
 #endif /* !defined TZ_MAX_LEAPS */
 
 #define SECSPERMIN	60
diff --git a/tests/time_test.cpp b/tests/time_test.cpp
index 0fb9bc0..483315d 100644
--- a/tests/time_test.cpp
+++ b/tests/time_test.cpp
@@ -181,10 +181,25 @@
   ASSERT_NE(static_cast<time_t>(-1), mktime(&t));
   ASSERT_EQ(0, errno);
 
-  // This will overflow for LP32 or LP64.
+  // This will overflow for LP32.
   t.tm_year = INT_MAX;
 
   errno = 0;
+#if !defined(__LP64__)
+  ASSERT_EQ(static_cast<time_t>(-1), mktime(&t));
+  ASSERT_EQ(EOVERFLOW, errno);
+#else
+  ASSERT_EQ(static_cast<time_t>(67768036166016000U), mktime(&t));
+  ASSERT_EQ(0, errno);
+#endif
+
+  // This will overflow for LP32 or LP64.
+  // tm_year is int, this t struct points to INT_MAX + 1 no matter what TZ is.
+  t.tm_year = INT_MAX;
+  t.tm_mon = 11;
+  t.tm_mday = 45;
+
+  errno = 0;
   ASSERT_EQ(static_cast<time_t>(-1), mktime(&t));
   ASSERT_EQ(EOVERFLOW, errno);
 }