About Rabi al-Thani
Rabi al-Thani (رَبِيع ٱلثَّانِي) is the fourth month of the Hijri calendar. Its name means “The second spring.” The fourth month, also called Rabi al-Akhir. It completes the pair of spring months in the traditional naming.
Like every Hijri month it has 29 or 30 days, determined in the Umm al-Qura calendar by the official tables and in the tabular calendar by a fixed arithmetic rule. Because the lunar month depends on the sighting of the new crescent, the exact first day can differ by a day from the calculated date.