diff --git a/libc/include/time.h b/libc/include/time.h
index 8e78949..17751d7 100644
--- a/libc/include/time.h
+++ b/libc/include/time.h
@@ -74,11 +74,12 @@
 struct tm* gmtime(const time_t* __t);
 struct tm* gmtime_r(const time_t* __t, struct tm* __tm);
 
-char* strptime(const char* __s, const char* __fmt, struct tm* __tm);
-size_t strftime(char* __buf, size_t __n, const char* __fmt, const struct tm* __tm);
+char* strptime(const char* __s, const char* __fmt, struct tm* __tm) __strftimelike(2);
+char* strptime_l(const char* __s, const char* __fmt, struct tm* __tm, locale_t __l) __strftimelike(2) __INTRODUCED_IN(28);
 
+size_t strftime(char* __buf, size_t __n, const char* __fmt, const struct tm* __tm) __strftimelike(3);
 #if __ANDROID_API__ >= __ANDROID_API_L__
-size_t strftime_l(char* __buf, size_t __n, const char* __fmt, const struct tm* __tm, locale_t __l) __INTRODUCED_IN(21);
+size_t strftime_l(char* __buf, size_t __n, const char* __fmt, const struct tm* __tm, locale_t __l) __strftimelike(3) __INTRODUCED_IN(21);
 #else
 // Implemented as static inline before 21.
 #endif