Compares two instances of DateTime and returns an integer that indicates whether the first instance is earlier than, the same as, or later than the second instance.
A signed number indicating the relative values of t1 and t2.
Less than zero t1 is earlier than t2.
Zero t1 is the same as t2.
Greater than zero t1 is later than t2.
Before comparing DateTime objects, ensure that the objects represent times in the same time zone.