Months are numbered from Nisan, the first month of the ecclesiastical
year, even though the civil year begins with Tishrei on Rosh Hashanah
(see HDate.getTishreiMonth for Tishrei-based numbering).
In a common year month 12 is Adar; in a leap year month 12 is Adar I
and month 13 is Adar II.
Hebrew months of the year (NISAN=1, TISHREI=7).
Months are numbered from Nisan, the first month of the ecclesiastical year, even though the civil year begins with Tishrei on Rosh Hashanah (see HDate.getTishreiMonth for Tishrei-based numbering).
In a common year month 12 is Adar; in a leap year month 12 is Adar I and month 13 is Adar II.
Example