Remind is a calendar program with a real expression language behind it: a Hebrew calendar, moon phases, sunrise and sunset, and date arithmetic that knows about weekdays, holidays and OMITted days. All of it is C, and all of it is reachable. remind-rb builds Remind's own sources into a shared library and binds them with Fiddle, so `moonphase(today())` and `sunrise('2027-06-21')` are Ruby calls rather than a shell-out and a parse of the output. Dates come back as Date objects, times as minutes, strings as strings. The Remind sources are vendored beside the gem, so the library binds the version it was built against rather than whatever is on the PATH.