increment the month and year in a date by one

[LEDIGRA]

I would like to put 3 command buttons and a textbox on a form. When the user click one button the day part of the date increment by 1. When they click the others the month and the year increnent by 1. I get the day part but cannot figure out how to increment the month and the year.

This is what I use to increment the day

newDay = newDay+1

newDay is the name of the text box with the date

Thanks for the help