Amajida, Shafira. “The Systematic Implications of the Hijri Calendar in the Caliph Umar Bin Khattab’s Period for the Present”. AL - AFAQ : Jurnal Ilmu Falak dan Astronomi 7, no. 1 (June 5, 2025): 57–66. Accessed April 18, 2026. https://journal.uinmataram.ac.id/index.php/afaq/article/view/11449.