What is the official calendar of Saudi Arabia?

The official calendar of Saudi Arabia is called the Umm al-Qura calendar, also called the Islamic Lunar calendar or Hijri calendar. This is the official calendar used by the Kingdom of Saudi Arabia and other Muslim countries. It is based on the lunar cycle, and each month begins with a new moon. The Umm al-Qura calendar has 12 months, each with 29 or 30 days. Each year consists of 354 or 355 days.