diff --git a/libziparchive/include/ziparchive/zip_archive.h b/libziparchive/include/ziparchive/zip_archive.h
index 098a9cb..fbc47db 100644
--- a/libziparchive/include/ziparchive/zip_archive.h
+++ b/libziparchive/include/ziparchive/zip_archive.h
@@ -47,9 +47,10 @@
   // Modification time. The zipfile format specifies
   // that the first two little endian bytes contain the time
   // and the last two little endian bytes contain the date.
-  // See `GetModificationTime`.
+  // See `GetModificationTime`. Use signed integer to avoid the
+  // sub-overflow.
   // TODO: should be overridden by extra time field, if present.
-  uint32_t mod_time;
+  int32_t mod_time;
 
   // Returns `mod_time` as a broken-down struct tm.
   struct tm GetModificationTime() const;
diff --git a/libziparchive/zip_archive.cc b/libziparchive/zip_archive.cc
index fb2a1d2..489fcb1 100644
--- a/libziparchive/zip_archive.cc
+++ b/libziparchive/zip_archive.cc
@@ -1299,6 +1299,7 @@
   return true;
 }
 
+// This function returns the embedded timestamp as is; and doesn't perform validations.
 tm ZipEntry::GetModificationTime() const {
   tm t = {};