Coin dating is the final basic attribution consideration. Here, the problem can be more difficult because the reading of a coin date is subject not only to the vagaries of numeric styling, but to calendar variations caused by the observance of various religious eras or regal periods from country to country, or even within a country. Here again, with the exception of the sphere from North Africa through the Orient, it will be found that most countries rely on Western date numerals and Christian (AD) era reckoning, although in a few instances, coin dating has been tied to the year of a reign or government. The Vatican, for example dates its coinage according to the year of reign of the current pope, in addition to the Christian-era date.
Countries in the Arabic sphere generally date their coins to the Muslim era (AH), which commenced on July 16, 622 AD (Julian calendar), when the prophet Mohammed fled from Mecca to Medina. As their calendar is reckoned by the lunar year of 354 days, which is about three percent (precisely 2.98%) shorter than the Christian year, a formula is required to convert AH dating to its Western equivalent. To convert an AH date to the approximate AD date, subtract three percent of the AH date (round to the closest whole number) from the AH date and add 622. The Muslim calendar is not always based on the lunar year (AH), however, causing some confusion, particularly in Afghanistan and Iran, where a calendar based on the solar year (SH) was introduced around 1920. These dates can be converted to AD by simply adding 621. In 1976 the government of Iran implemented a new solar calendar based on the foundation of the Iranian monarchy in 559 BC. The first year observed on the new calendar was 2535 (MS), which commenced March 20, 1976. A reversion to the traditional SH dating standard occurred a few years later.
Several different eras of reckoning, including Christian and Muslim (AH), have been used to date coins of the Indian subcontinent. The two basic systems are the Vikrama Samvat (VS), which dates from Oct. 18, 58 BC, and the Saka era, the origin of which is reckoned from March 3, 78 AD. Dating according to both eras appears on various coins of the area.
Coins of Thailand (Siam) are found dated by three different eras. The most predominant is the Buddhist era (BE), which originated in 543 BC. Next is the Bangkok or Ratanakosindsok (RS) era, dating from 1781 AD; followed by the Chula-Sakarat (CS) era, dating from 638 AD. The latter era originated in Burma and is used on that country's coins. Other calendars include that of the Ethiopian era (EE), which commenced seven years, eight months after AD dating; and that of the Jewish people, which commenced on Oct. 7, 3761 BC. Korea claims a legendary dating from 2333 BC, which is acknowledged in some of its coin dating. Some coin issues of the Indonesian area carry dates determined by the Javanese Aji Saka era (AS), a calendar of 354 days (100 Javanese years equal 97 Christian or Gregorian calendar years), which can be matched to AD dating by comparing it to AH dating.
The following table indicates the year dating for the various eras, which correspond to 2009 in Christian calendar reckoning, but it must be remembered that there are overlaps between the eras in some instances.
|Christian era (AD)
|Muslim era (AH)
|Solar year (SH)
|Monarchic Solar era (MS)
|Vikrama Samvat (VS)
|Saka era (SE)
|Buddhist era (BE)
|Bangkok era (RS)
|Chula-Sakarat era (CS)
|Ethiopian era (EE)
|Javanese Aji Saka era (AS)
|Fasli era (FE)
|Jewish era (JE)
Coins of Asian origin - principally Japan, Korea, China, Turkestan and Tibet and some modern gold issues of Turkey - are generally dated to the year of the government, dynasty, reign or cyclic eras, with the dates indicated in Asian characters which usually read from right to left. In recent years, however, some dating has been according to the Christian calendar and in Western numerals. In Japan, Asian character dating was reversed to read from left to right in Showa year 23 (1948 AD).
Some coins carry dates according to both locally observed and Christian eras. This is particularly true in the Arabic world, where the Hejira date may be indicated in Arabic numerals and the Christian date in Western numerals, or both dates in either form.
Timing differentials between some era of reckoning, particularly the 354-day Mohammedan and 365-day Christian years, cause situations whereby coins which carry dates for both eras exist bearing two year dates from one calendar combined with a single date from another.