Limitations Uses Unix timestamp as base unit (seconds since 1970-01-01, 00:00 GMT) Only 32 bit signed integers for timestamps (1901 to 2038) Limited to only positive numbers on some Operating Systems (1970 to 2038) ~strtotime()~ is buggy and its implementation is very complex No way of dealing correctly with timezones Some functions are Operating System dependent *Avoid* functions that deal with timestamps as much as you can!