The Solar Hijri system, or SH, is almost exclusively used in Iran and Afghanistan and their coinage. The system was developed by Omar Khayyam, a Persian mathematician, astronomer, and poet who differed from the Lunar Hijri system by following the sun rather than the moon. The Solar Hijri system is astronomically accurate year to year, in which a year has 12 months and 365 or 366 days. The difference being that the first six months of the year each have 31 days, the next five months have 30 days, and the final month will have 29 or 30 days depending on leap years. Like the Lunar Hijri system, the start corresponds to Hijra, the year the Prophet Muhammad and his followers migrated from Mecca to Medina. Date conversion to the Common Era dating usually adds 621 to the SH date.
Afghanistan started using the Solar Hejira in AH1337 or 1919 CE, and the date now became SH1298. Iran first started using the SH dating for coins in AH1344 or 1925 CE. Iran under Shah Mohammad Reza Pahlavi changed the original date of the Solar Hejira calendar to the first year of the reign of Cyrus the Great. Under this new system, SH1355 became MS2535 or 1976 CE. This change was short-lived, and with the revolution in 1979, the calendar reverted to Solar Hijri.
At PCGS, we have worked hard over the last few years to update our system to add the additional coin dates on the labels and website information. For coins that have an SH date, we will note the SH date and the Common Era date conversion, for example, SH1301 (1922). For coins that are dated under the MS date system, we will also add a Common Era conversion, such as MS2537 (1978). With coins bearing joint dates, we will label them as, say, SH1350-1971.