I'm writing an extension, Extension:RevertRange, that lets a sysop enter a starting timestamp and an ending timestamp for reversion of a user's actions. (e.g. a bot might have misbehaved and now it's desired to undo everything that it did.) What's the best way to have the sysop enter such a timestamp? My current implementation has him enter a 14-digit timestamp, but humans are not used to that kind of format, usually.