Handling date and time in PHP makes most coders nervous. There are a bunch of functions playing arround with system time and timezone features, using UNIX timestamps and therefore are very limitted in application. At least I know a lot of guys born before 1970. Native Unix timestamps may be of great use for system level stuff like logging information or handling object lifetime, but not for real world scenarios: handling user age or historical events is impossible with 32 bit UNIX timestamps.