#set iCal to use jewish calendar
defaults write com.apple.iCal AppleLocale he_IL@calendar=hebrew

#set ical to use Goyish calendar so it works with exchange 
defaults write com.apple.iCal AppleLocale he_IL@calendar=gregorian

#set the whole system to use Jewish cal
defaults write -g AppleLocale he_IL@calendar=hebrew

OSX 10.6 adds exchange support , but breaks if you use jewish calendar , this will fix it.

Set calendar type only for ical

osx

Bash