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, Zou'iqu'ad, 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*
is analogous to converting Celsius-scale temperatures *C* to Fahrenheit
values *F*. In both situations there is a relative shift of the origin and a difference in the
size of the units. The *hejri* (Persian rendering) system is based on a lunar reckoning of the solar year
that is about eleven days shorter than the actual 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 *Hejri* months thus do not maintain a fixed correspondence with the Western months
or with the months of the Hindu solar calendar.

While the approximate formula cannot be used for
the actual dating of covers, it works better than one might imagine for our postal period.
Thus to test the example at the top the screen (1 *muharram* 1276 ~ 31 July 1859),
the formula gives W ≈ 1859.54 AD ~ 18 July 1859, which is merely a couple of weeks
shy. In a pinch, such an estimate might even be good enough for some purposes.

While the temperature scales cross at the well-known point
–40°F = –40°C, the crossing on the calendars is rather a moot issue:
*W* = *H* ≈ +20,000 AD, give
or take a millennium. One trusts that none of these systems will be in use at that time.