Why do my files have a last modified timestamp of January 1, 1980?

I’m working in Python with a number of libraries at play.

I have a group of files on a Linux server that have the last modified timestamp of midnight on January 1, 1980 (unix timestamp 315532800.0). The last changed timestamp however is recent. What could have caused this?

In particular, Jan 1 1980 is a suspiciously round number, but not one of the usual suspicious round numbers.

Answer

The culprit is the Python zipfile library. If you don’t pass a second parameter to ZipInfo, it defaults to Jan 1, 1980: https://docs.python.org/3/library/zipfile.html#zipfile.ZipInfo