Hi all,
I thought of contributing to this fantastic forum, so this is a guide that I am sure many people know about, but I am writing this to those people out there who might face these Islamic dates while coin collecting.
Let's start by defining the Islamic dates, also known as Hijri dates.
The Islamic date started when the Prophet Mohammad, who preached the Islamic message, immigrated from Makkah to Yathrib, currently known as Al'Madinah Al'Munawwarah.
His immigration was the result of the Hatred and Mock he received from his home town Makkah, so his destination (Yathrib) marked the beginning of the Islamic Uprise.
The Islamic year started AD 622.
If you ever had a coin with numbers in Arabic that you did not know translates to which Gregorian (AD) date, then this might come handy.
Here is a list of Numbers translated into numerals that are on your coins:

These numbers' shapes might differ very slightly, but it can still be easily recognizable.
Although Arabic is written from right to left, in contrast with English's left to right, the Islamic dates (numbers) are written from left to right.
So AD 1880 can be written as "١٨٨٠Ù." (Gregorian), and "١٢٩٧هـ" (Hijri year).
If "Ù." appears after the date, then the date is Gregorian.
If "هـ" appears after the date, then the date is Hijri (Islamic).
Quote:
Note:
AH refers to "After Hijra", which is the Islamic date.
AH is written after the numbers, so the Islamic year 1392 is written as 1392 AH, unlike the Gregorian date (AD) which is written before the numerals.
Many coins do not write the Arabic letters to signify either a Gregorian date or a Hijri date, so you might just read the numerals. It is obvious if the date is Gregorian or Hijri, since coins will obviously look old or new.
Quote:Quick Note:
This is something that many do not know about, Arabic numbers (٠١٢٣٤٥٦٧٨٩) are not really Arabic, they originate from India.
Arabic numerals are in fact the numbers that we use everyday (0123456789).
Research it for more information.
A great start would be Wikipedia.
https://en.wikipedia.org/wiki/Arabic_numerals Finally, there are many ways in which you can translate the Hijri dates into Gregorian (AD) dates.
You can just write the Hijri date into google.
But the most efficient way to convert the dates is using this tool:
http://www.islamicfinder.org/dateCo...ate_result=1Just input the Hijri date and proceed.
Here are 2 examples to further explain the Hijri dates:
1- This is a coin from my country:

The date on the left "١٩٧٣" translates to "1973" which is obviously Gregorian due to the fact that the Hijri date is still in the 15th century.
The date on the right "١٣٩٣" translates to "1393" which is obviously Hijri due to it's modern design and look.
2- This is an Ottoman coin:

The date "١١٧١" translates to "1171" which is a Hijri date due to its known design. 1171 AH translates to AD 1757.
Thank you for your time and I hope this guide helps you in a way or another.
