in GMime 4.0, timestamps should use some sort of robust/native GLib representations

[dkg]

This is an API change recommendation for GMime 4.0. Rather than relying on the problematic time_t legacy, GMime should take advantage of GLib's native forms of timestamping when representing signatures, expirations, etc.

Anyone using GMime is already using GLib, so GMime should let GLib do the heavy lifting here.