how to minus 7 days from current date time and get its date

Can somebody please let me know, How to create a variable of type ‘date and time’ whose value is equal to the 1 week before date .  [%DayLength%] is working with only xpath but while creating a variable not able to use it .   
1 answers

Have a look at the AddWeeks function. Just pass in the current date time and put in -1 for the amount of weeks you want to add to go back.