What is "backdated"

Usage examples of "backdated".

As she got into the passenger seat she passed him the backdated note he had asked her to write.

It certainly would have been more expedient had you previously filled out an application at the administration office, but I may he able to slip through a backdated STA111.

After a five-minute interview Andy was talking to girls in the playground while a pallid headmistress backdated his entrance forms.