Hi there,
In any case, there is not currently a user configurable option to make this change - it would require a developer to make custom changes to the widget.
There are 2 different calendar / datepicking widgets we use in AtoM - one from the Yahhoo User Interface (YUI) library, and the other from the JQueryUI library.
For example, there' s a datepicker in the Accession edit page, for setting the acquistion date. The library we use for this calendar widget is of the YUI library - specifically the YAHOO.widget.Calendar, found here in our code:
And here is one of the places we instantiate it:
I don't know if it's possible to configure this to display an Islamic calendar or not, but there are some docs here that you could look at for more information:
The other library is the JQuery widget, which we use in the Advanced search for archival descriptions. Here is where the JQueryUI library is maintained in AtoM:
Here's where we initialize it:
And here's some more info on the widget:
Good luck, and let us know how it goes!