Converts between the Gregorian and Hijri calendars in both directions, one date per line (direction auto-detected from an H/AH marker, or forced). Umm al-Qura is Saudi Arabia's civil calendar and the default (browser ICU data, 1300–1600 AH); civil and astronomical are the arithmetic tabular calendars used by many software systems. Every result states which rule was used, because calendars based on actual moon sighting can begin a month a day earlier or later than any rule-based calendar. Everything runs locally.