Add FROM and UNTIL to trigdates

Remind needs some information when the SATISFY could evaluate to true or
it will give up with "Can't compute trigger".

Thanks to Dianne Skoll for the proposal.

remind.py

@@ -364,12 +364,15 @@ def stdin_to_vobject(self, lines: str) -> Component:
     @staticmethod
     def _parse_rdate(rdates: list[date], repeat: int = 1) -> str:
         """Convert from iCal rdate to Remind trigdate syntax."""
+        rdates = sorted(rdates)
+        start = rdates[0].strftime("FROM %Y-%m-%d")
         trigdates = [
             (rdate + timedelta(days=d)).strftime("$T=='%Y-%m-%d'")
             for rdate in rdates
             for d in range(repeat)
         ]
-        return f"SATISFY [{'||'.join(trigdates)}]"
+        end = (rdates[-1] + timedelta(days=repeat-1)).strftime("UNTIL %Y-%m-%d")
+        return f"{start} {end} SATISFY [{'||'.join(trigdates)}]"
 
     @staticmethod
     def _parse_rruleset(rruleset: Any, duration: timedelta) -> str | list[str]: