See Access Help regarding the DateAdd Function.
To Add one day to todays date: DateAdd("d", 1, Now())
To Subtract one Day from todays date: DateAdd("d", -1, Now())
To Add one Week to todays date: DateAdd("ww", 1, Now())
To Subtract one Week from todays date: DateAdd("ww", -1, Now())
To Add one Month to todays date: DateAdd("m", 1, Now())
To Subtract one Month from todays date: DateAdd("m", -1, Now())
To Add one Year to todays date: DateAdd("yyyy", 1, Now())
To Subtract one year from todays date: DateAdd("yyyy", -1, Now())
just for a start.....
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