Qoute from office help under Cat Format dates using alternate
calenders:(Enter a date in a cell and have Excel interpret it as a Hijri date
instead of Gregorian.

Type A or a in front of the date entry€” for example, enter the short date
'a9/25/20', which will be interpreted as Hijri date 9/25/1420 (this is
Gregorian date 1/1/2000). If the cell is unformatted, it will be assigned the
number format 'B2m/d/yyyy' and the value will be displayed as 9/25/1420.)
Sorry but it doesn't work it returns a text Value
My region settings is English US - my deflt lang is English and Arabic is
Enables as second language Thanks :