The standard package for working with dates and times in Haskell, time, is awkward. That's a subjective judgment, but over the years there have been few areas more frustrating than trying to do pragmatic things with calendars and clocks.
This package represents some opinionated approaches to working with times and dates. It also is just a place to collect some hard-won idioms for converting between things.
You absolutely do not need to use this; if you can make sense of the basic time and calendar types available by default then by all means have at it.
This package was seeded using the TimeStamp type originally from the Vaultaire project, a time-series database for systems metrics. That type was originally implemented as a shim on top of base's time package; limitations there (notably base being misleading about precision) have led it to be reimplemented atop of the very complete (but also somewhat complicated) hourglass library.
Our original use was wanting to conveniently measure things happening on distributed computer systems. Since machine clock cycles are in units of nanoseconds, this has the nice property that, assuming the system clock is not corrupted, two subsequent events from the same source process are likely to have monotonically increasing timestamps. And even if the system clock goes to hell, they're still decently likely to be unique per device. Make for good keys.
So the TimeStamp type herein is nanoseconds since the Unix epoch; which in (signed) 64 bits means that you can represent times between early in the morning of 21 September 1677 through just before midnight on 11 April 2262. The primary use isn't doing calendaring, though; it's just working with machine generated timestamps in distributed systems.
Yes, at present that's all it is. A newtype over Int64, and some convenience functions. Hopefully more common idioms will land here in due course.