This online calculator adds date components to a given date. It also produces the result for inverse operation (subtraction). Finally, using the calculator, you can change the time zone for resulting date.
This is generalised version of several date modification calculators, listed on this site. In particular this calculator can modify a given date by addition or subtraction the following date components:
Besides date and time arithmetics the calculator can change time zone of the input date to take in account the time difference in the different corners of the planet.