The time crate is the underlying crate which chrono uses for its
various operations.
Unfortunately, chrono is unmaintained and older versions of the time
crate have security vulnerabilites[0] which are unfixed in chrono[1].
The medallion code does not use any chrono-specific features and all
uses of it could be trivially replaced with the underlying time
structs.
Note that this change adds calls to `expect`. Where these calls are
made, the previous chrono functions also panicked internally if
out-of-range values were passed.
We noticed this issue while doing a similar refactoring in a program
that also uses medallion[2].
[0]: https://rustsec.org/advisories/RUSTSEC-2020-0071.html
[1]: https://rustsec.org/advisories/RUSTSEC-2020-0159.html
[2]: https://cl.tvl.fyi/c/depot/+/5311
