On Windows 10 there are 2 available calendar formats we can choose; Gregorian
Calendar and Hijri Calendar.
Gregorian calendar is the default date format worldwide that we all familiar
today meanwhile Hijri calendar is more common among Muslims or in Islamic
states.
To switch to Hijri calendar, first open "Settings" from the
start menu and select "Time & Language" from the list
of the settings as shown in the picture below.
On the next page, search for "Date, time, & regional formatting"
located on the right side of the window.
Scroll down to the bottom of the page and click on "Change data formats".
Lastly, select Hijri Calendar from the Calendar dropdown menu on the new page.
Windows will show Hijri date upon switching.