Saudi Year Conversion Question

The Islamic year is a few days shorter than the Gregorian year, so they only very occasionally line up just right. (A recent case when they did was 1429/2008.) Normally an Islamic year would include parts of two different Gregorian years (and vice versa). So there's no real standard conversion - not even the "add/substract this number" sort of standard conversion (because it slips up by approximately three years per century).

The year 1397 is actually pretty close to lining up just right, starting in late December 1976 and ending in mid-December 1977. (The year 1396 does in fact fit fully in 1976.)
The year 1400 starts in late November 1979 and ends in early November 1980.

I guess Numista probably goes by which part of the year is larger (I think - I never really checked), while NGC presumably goes by the start of the year. (If so, I wonder what they use for Israeli years, which consistently start around late September.)
IMHO, Numista's versions make more sense this time, but really a case could probably be made for either.

Thank you for your responses. Albert - that sounds interesting, will give it a try.

Of course the easy way to convert years is with this online tool:

http://www.iranian-calendar.com/DateConverter

But it's great to know the methodology.

I agree. I've been remounting some Saudi coins and it is very convenient, comes second nature now. Only had one conversion which didn't agree with the published data.

The link 999fine posted is fine for modern coins, and having both the regular Islamic and Iranian calendars is helpful, but if you need older dates converted (say, on Ottoman Empire coins) then you'll have to use a different website. This is the one I use as it goes all the way back to AH 1; just type in the year you want to convert, and it automatically replies with what AD date Islamic New Year fell on in that year.

There will, on occasion, be differences of opinion as to how to convert AH dates to AD, because of the moving nature of Islamic New Year in the AD calendar. For example, if a coin is dated "1415"; AH 1415 began on 10th June 1994 and ended on 31st May 1995. Statistically, it's more likely that such a coin would have been struck in 1994, so "1994" is the usual conversion date. But if it was struck late in 1415, then the actual conversion date wold be 1995.

The Islamic year is shorter than ours, so it is slowly "catching up". We're all looking forward to the year 20,874 when the two calendars will finally be in sync.

Technically I had small error in the formula I use just for simplicity. It's really AH date minus 3.03% instead of just 3%. I imagine that small extra fraction might come in handy as you go farther back in time. Don't really know- just thinking out loud.
And I also know about some other opinions about conversion dates. I use +622, but some published coin books on Dating Guides for the Eastern World use the number 621.

Getting a good grab on these date conversions can be meaningful to some collectors. There does seem to be a lot of error written on some seller's coin holders found online and at coin shows. Getting the date right or wrong can mean a coin for your collection was issued in the name one ruler or a different one. Sometimes one dynasty or one government can end on one year and begin on the next, or even within the same year. So if you don't get the date right, it can mean you have a wrong coin in the collection.

Good discussion! I believe that its understanding of details such as these benefit the hobby and the scholarly pursuit of numismatics on the whole. Glad to see that.

Also, very nice presentation of your collection 999fine!

Would love to have such beautiful handwriting!