Nessma Diab 

I wonder if the way to address this is through the calendar type in your windows settings?  Trados Studio most likely takes these settings from windows as I don't believe we have options for the calendar type in Trados Studio:

Thank you for your assistance, Paul. Unfortunately, this solution did not resolve the issue. I changed my region and regional format settings, set the calendar to Gregorian as indicated in the first 2 screenshots, and even restarted my computer. However, not only did this fail to correct the date conversion, but it also created further inconsistencies: Trados retained the Gregorian year and day while converting only the month to Hijri as shown in Screenshot 3, resulting in an incorrect date display (e.g., a nonexistent year 2026 in the Hijri calendar).

Screenshot 1

Screenshot 2

Screenshot 3

Nessma Diab 

ok - out of interest did this use Gregorian correctly in previous versions?  I didn't test yet bit perhaps you know?

I have logged this with the support team because I don't know how to help more with this one.  I'll let you know when they come back to me.

Nessma Diab 

ok - out of interest did this use Gregorian correctly in previous versions?  I didn't test yet bit perhaps you know?

I have logged this with the support team because I don't know how to help more with this one.  I'll let you know when they come back to me.

Nessma Diab 

I have spoken to Support and It seems that Studio always used the Hijri calendar for Arabic (Saudi Arabia).  The behaviour is the same in Studio 2015.  Support logged an enhancement request for Development (our reference CRQ-40362) so they can consider switching to the Gregorian calendar or adding the option for customers to choose between the two.

So for now your best option would be to choose a different variant if you need the Gregorian calendar.

Thank you so much, Paul! I really appreciate it! 

Yes, there is always a workaround, but having the option to choose the calendar type would be great.