Include <stdbool.h>. Use bool where appropriate, instead of int. (my_strftime): Do not mishandle years close to INT_MAX, by doing the right thing even if adding 1900 would overflow. Similarly for tm_mon + 1 and tm_yday + 1. Make %Y always equivalent to %C%y, and similarly for %G and %g. (DO_NUMBER, DO_NUMBER_SPACEPAD): Set digits to d, not a conditional. (DO_SIGNED_NUMBER): New macro. (my_strftime) [HAVE_TZNAME]: Don't dump core if tp->tm_dst > 1.