We should be able to do more with dates. In particular:

Logging:

We should support a -d switch to show log entries from particular dates. Formats we should support:

We'll need to scan the entire changelog as there's no guarantee that there's any date ordering.

Update/Revert:

Again, we should support a -d switch, which results in scanning the log for the first matching changeset. This is usually what people want.

Here, and elsewhere, we should allow dates without hours, minutes, or years.