touch time format (fwd)

[hcchin]

    I see that thre is an -d time option form man touch, but I try a few 
format but not succeeded, any one know the time format?

$ touch -d 12:34 file1
touch: invalid date format `12:34'

$ touch -d "12 March" file1
touch: invalid date format `12 March'

$ touch -d "12 Mar" file1
touch: invalid date format `12 Mar'

$ touch -d 12-05-2000 file1
touch: invalid date format `12-05-2000'

What are the valid format ?