I know how to get a file's mtime in epoch format:
stat --format=%Y <file>
But I have not been able to figure out how to set a file's mtime in epoch format. The touch(1) man page appears to only accept a "timestamp" value (more-or-less fixed format which uses months, days, hours, minues, etc) or a "mostly free format human readable date string".
Is there another utility I should be looking into?