Javascript needs to be enabled. This calendar conversion utility is based on the charts in Staal’s text. The conversions are believed accurate to about a day one side or the other. For the month names, which are here based on an Urdu transcription, one will find in the literature a wide range of renderings of varying fidelity and consistency that draw also from the Arabic and Persian. So for one of the months, prepare to see such variations as zī qa'dah, zīqād, Dhiqada, zigoda, Dhaqadah, zelqa'de, ziqa'ad, Dhu-al-Qa'da, zu-lqa'de, Zu-lqada, Zulgada, zi'l-ka'da, Thw al-Qi'dah, and others for which a more imaginative font set is needed.

Converting these dates, anno hegirae H, to Western dates W using a linear approximation is analogous to converting Celsius-scale temperatures C to Fahrenheit temperatures F. In both situations there is a relative shift of the origin and a difference in the size of the units. The Muḥammadan year is based on a lunar reckoning that is about eleven days shorter than the solar year. So we may compare:

F = 32°F + (9/5)C
W ≈ 622 AD + (354/365)H.

Just as 9/5 is the factor by which the centigrade degree is larger than the Fahrenheit degree, the (approximate) factor 354/365 accomodates the fact of the “short” lunar year. Lunar months thus do not maintain a fixed correspondence with Western months or with Hindu solar months. This overly simple formula cannot be used for the actual dating of covers, though it actually works better than one might imagine. It may be amusing to calculate where the scales would cross: Of course –40°F = –40°C on the temperature scales. On the calendars, W = H ≈ +20,000 AD, give or take a millennium. One trusts that none of these systems will be in use at that time.