It seems that mktime does what is required here. Certainly timegm() can not be used because it is not available on all systems (most notably, win32).
It seems that mktime does what is required here. Certainly timegm() can
not be used because it is not available on all systems (most notably,
win32).

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl