Time math in Delphi

Question

I have a pretty unusual problem (for me). I am writing an application that will allow a user to change their system time forward or back either by explicit date (change my date to 6/3/1955) or by increment using buttons (go forward 1 month).

I'm writing this to help some of my users test some software that requires jumps like this in order to simulate real world usage of a billing system.

Changing the time in Delphi is of course very easy:

SetDateTime(2008,05,21,16,07,21,00);

But I'm not sure if Delphi (2006) has any built in helpers for date math, which is one of my least favorite things :)

Any suggestions for the best way to handle this? I'd prefer to stay native as the winapi datetime calls suck.

Thanks!

Answer 1

As mentioned by gabr and mliesen, have a look at the DateUtils and SysUtils units, useful functions include.

• IncDay - Add a or subtract a number of days.
• IncMonth - Add a or subtract a number of months.
• IncWeek - Add a or subtract a number of weeks.
• IncYear - Add a or subtract a number of years.
• EncodeDate - Returns a TDateTime value from the Year, Month, and Day params.

Answer 2

There is plenty of helpers in the DateUtils unit.