Anyone with correct Mac OS X calendar prefs knowledge… …please help!

The click-spacer "contact ring” on the bottom of my older-version Mac mouse broke, and I just only have the top view from the mouse prefs to incl. as an attachment for you to determine which version I’m using.

I inadvertently changed my calendar?display to Islamic from our common Julian(?) display. ?Trying to use the broken mouse may have selected the Islamic display.

Now though, I need to?change the calendar?display back to Julian! ?Or I got borked/hacked by some not-so-friendly nearby person - but no one admits knowing arabic [AIR-ah-bik], and yet they continued to correct my pronunciation with [ah-RAH-bik]).

PLEASE HELP !! ?

-russ preston