Islam's Lunisolar Calendar and the Celestial Year-Clock

This book shows that the Prophet Muhammad ﷺ used and taught a lunisolar calendar in which the month of Ramadan always contained the southward equinox and the Hajj was always at the winter solstice. The evidence for this comes from the Holy Qur'an, the hadith and the sirah.
The strictly lunar calendar currently in use, with months that drift through the seasons, was instituted during the time of the second caliph 'Umar ibn al-Khattab.
The nasi' of verse 9:37 in the Qur'an referred not to a postponed month, but to the head of the supreme rabbinical council who controlled the starts of months and years in the Jewish calendar.
The book describes the well-known synchronization of the lunar and solar cycles every nineteen years, while also explaining for the first time how a tabular calendar like the Jewish calendar gradually goes out of season by omitting necessary shifts in the order of leap years every 341 years on average.
The book features:
- primary source passages in Arabic and Hebrew with English translation
- a table with Julian dates of major events in the Prophet's life
- lunar month tables for the present day and during Muhammad's prophethood
- an enumerated list of Qur'an verses containing the words yaum (day), shahr (month) and sanah (year), indicating the Qur'an's numerological endorsement of the lunisolar calendar
- illustrations of the 19-year cycle and the celestial year-clock
- diagram showing leap-year shifts over a period of 6479 years
- a proposal for keeping the slowly drifting Jewish calendar in season from now on
- glossary of relevant calendrical and Islamic terms
- bibliography
- indexes of Qur'an verses cited and of personal names mentioned