Nadia,

I take it this is still part of the offical document (marraige contract) you are translating (watch out, we might be able to piece up the entire document :)). If so, I suggest you do the following:

Convert the date to Gregorian. شهر جمادى الثاني سنة 1423 هجرية is August 2002. Place the date in situ within the text, and add a translator's note in the footnote as follows:

The date is translated from the Islamic Hijri calendar [orginial date: Jumada ath-thani 1423 Hijri].

Or retain the Hijri date in text like so:

Jumada ath-thani 1423 Hijri

and add a translator's note in the footnote like so:

Islamic calendar date equivalent to: August 2002.


This is sound practice in the translation of official documents. The target audience would not have a clue what Jumada ath-thani 1423 Hijri and variants are, were these to be left unexplained in the translation.

For a handy online Islamic calendar converter, check these links:

Primary:
http://www.cs.pitt.edu/~tawfig/convert/convert.cgi

Using this converter, if you are also citing the day in the date, make sure you add a cautionary note that there is a small error margin of one day.

Secondary (just if you don't know the sequence of hijri months), the months are numbered:

http://wwwcgi.umr.edu/cgi-bin/cgiwrap/msaumr/hijri

Cheers
Ali