back·date 
/ˈbækˌdeɪt/ verb
back·dates; back·dat·ed; back·dat·ing /ˈbækˌdeɪt/ verb [+ obj] 1 : to give (something) an earlier date than the actual date : antedate
▪ backdate a check 2 : to say that something began or became effective at a date earlier than the current date
▪ an increase in salary backdated to the beginning of the year
▪ backdate a check
▪ an increase in salary backdated to the beginning of the year
