Like any good programming language PHP needs a way to handle dates. Theres loads of functions and ways that handle date in PHP.
Heres a list of few important functions:
time() returns the current Unix timestamp
date() retruns a timestamp in a given format, uses time() if no timestamp is given
date_create() returns a DateTime object, it needs a datetime string and optionally a timezone.
date_date_set() sets the given date to a new one with given ints, corresponding to year, month and day
date_diff() returns the diff of 2 given DateTime objects
date_format() returns a given DateTime object in a different given format
date_modify() Alter the timestamp of a DateTime object by incrementing or decrementing in a accepted format
timezone_offset_get() gets the offset to GMT of a given date with a given timezone object
A Date or Time string can be alot of things like “now”, “today”, “in 5 days”, “first day of June 2009”. Or simply
It is parsed by a parser if needed and turned into a date and time of your choice.
The formats and how its parsed is very interesting.