Timestamping Service: Existing Services or Software Project?

[Johannes Graumann]

Hi all,

I've done some superficial googleing, but didn't get far ... so I'm asking
here:
Is anybody aware of a software project implementing a time stamping service
via gnupg: you submit your signature of a file and it comes back signed by
a time stamping authority, which goes to some length to make sure there
machine time is semi-correct, thereby saying that you signed this file
before time X?

Thanks for any hints, Joh