The argument 
to CalendarChange converts between Western (Gregorian) dates and Jewish dates. The Gregorian date of Israel's independence is May 14, 1948:
| Out[2]= |  |
Because the Jewish calendar has a leap month preceding Passover, Mathematica uses a numbering starting with Nisan, the month of Passover:
Israel's independence was declared on the 5th of Iyar, 5708.
In Mathematica numbering, Tishrei, the first month of the Jewish year, is number 7.
| Out[2]= |  |
| Out[3]= |  |
By definition, Yom Kippur cannot fall on a Friday or Sunday:
| Out[2]= |  |
Because of the leap month, Jewish dates can vary by up to a month in the Western calendar. The Western and Jewish anniversaries of Israel's independence differ greatly:
| Out[2]= |  |
| Out[3]= |  |
The Jewish calendar follows a 19-year cycle. Western and Jewish anniversaries will correspond almost exactly every 19 years:
| Out[2]= |  |
| Out[3]= |  |
, you first need to load the Calendar Package using 
.
is a value for the Calendar option, and can be used as an argument to CalendarChange.
