A few weeks ago we wrote about the 5 steps to estimate the price on sale of a coin, being the coin identification the first of them. One of the crucial things in the identification process is its minting date, for that reason, we have created a series of pots to give you the keys to guess that date.
There are ancient coins in which there is no minting date, however the most common thing is to find it included as part of the design of the coin. Finding this date is a hard task in old coin or those who have very strong sings of wear. But even the contemporary coins, the identification of the minting year might cause some problems.
In this post we will go through the different calendars and tipografies used in the contemporary coin dates, after the end of the XVIII century. Most of the coins use the Latin alphabet and the Gregorian calendar, very easy to identify, but this is not always the case. For example, the coins belonging to Arab countries such as Morocco use the Muslim calendar for the minting date, so we should make the proper conversion.
Few coins with different calendars:
In order to know the minting date of a coin, the first task is to identify the alphabet that is being used. Most of current coins (Euro, US Dollars, Russian Rubles, Mexican pesos...) the Latin numeration is used, however some other ways of numbering also exist.
Here you have a table with the equivalences between alphabets:
If you want more information regarding the different numeration systems you can find it here:
But that is not the end of our problems, once we have finished determining the alphabet used to date a coin and we have been able to recognise the characters that compose that date we need to convert it depending on the calendar that was used.
At present most of the planet earth follows the same calendar, but this has not been always like that. Along history different structures to measure time have risen and coins have been affected by them. This way, the dates on the coins might follow any of the following calendars:
The Gregorian calendar is original from Europe, currently used in an official way in almost every part of the world. Named this way because its promoter was the pope Gregorian XIII, substituted in 1582 the Julian calendar, used since Julio Caesar instaurated it in the year 46 b.c.
It is the calendar used for the minting years in most of the contemporary coins.
Few coins dated with this calendar:
Islamic Chronology starts in the occidental year of 622 (16th of July), year in which Muhammed runway to the city of Mecca, starting the Hijra. There are two variants of this calendar depending on if you use the sun or the moon as a reference.
Is the calendar used in almost all the Islamic countries, except for Iran and Afghanistan as we will see in the following lines.
The Arabic year is lunar and not solar, so it is not composed of 365 days or 364 in leap years. On the contrary it is based in lunar cycles of 30 years (360 lunar cycles, of Sumerian tradition). The 30 years of the cycle is divided in 19 years of 354 days and 11 years of 355 days. The years of 354 days are called simple years and are divided in six months of 30 days and another six months of 29 days. Years of 355 days are called leaps years and are divided in seven months of 30 days and another five of 29 days. Years and months alternate each other.
Summing up, a full cycle of 33 Muslim years are equivalent to 32 Gregorian years.
Taking that into account, if we want to determine the year to which year of the Gregorian calendar corresponds a certain year from the hijra, we need to calculate the 3 per cent of this last one, and subtract it from the year then sum the result to the starting year of the hijra, the 622.
Let’s apply an example to a coin:
- ١ -> 1
- ٣ -> 3
- ٩ -> 9
- ٠ -> 0
Therefore we want to calculate the corresponding occidental year that corresponds to the Islamic 1390, we should make these calculations:
3% de 1.390 = 41.7 (42)
1.390 - 42 = 1.348
1.348 + 622 = 1.970
There is another form of calculating the correspondence. It consists on multiplying the Islamic year by 0.970224 and add 621.5774. From the result the cipher on the left of the decimal point is the year after Christ, and the decimal fraction multiplied by 365 is the day of the year. Our latest example would be:
1390 * 0.970224 = 1348,61136
1348,61136 + 621.5774 = 1970,18876
0,18876 * 365 = 68,8974
According to this calculation the Islamic year 1390 corresponds to the occidental year of 1970. However, due to the fact that Gregorian years and Islamic years have not the same length, nor they start nor they finish in the same date, this calculation is not 100% exact, so for that we would have taken into account not only the year but also the month.
Next week we will continue with the part two of this series!