Javadoc
Adds deviation definition. The year and month sepcifed should be the
caluculated Hijrah year and month. The month is 0 based. e.g. 8 for
Ramadan (9th month) Addition of anything minus deviation days is
calculated negatively in the case the user wants to subtract days from
the calendar. For example, adding -1 days will subtract one day from the
current date. Please note that this behavior is different from the
addDeviaiton method.