Tonda PF Hijri Perpetual Calendar
Description
The TONDA PF Hijri Perpetual Calendar represents a modern interpretation of the Tabular Islamic calendar, which was devised by Muslim scholars and astronomers in the 8th century. This ancient system enabled historians to convert dates from the Islamic calendar to the Gregorian calendar, facilitating the creation of the Hijri Perpetual Calendar. The inception of the Hijri calendar is dated back to 622 CE, commemorating the Prophet Muhammad's migration (Hijrah in Arabic) from Mecca to Medina, presently within the borders of Saudi Arabia.
Differing from the solar-based Gregorian calendar and the lunisolar Chinese Xiali calendar, the lunar Hijri calendar follows the moon's phases. This results in a repeating 30-year cycle, with each year comprising 12 months that vary between 29 and 30 days. Within this cycle, there are 19 common years that have 354 days and 11 leap years that span 355 days.