Month: Among the Egyptians the month of thirty days each was in use long
before the time of the Exodus, and formed the basis of their
calculations. From the time of the institution of the Mosaic law the
month among the Jews was lunar. The cycle of religious feasts
depended on the moon. The commencement of a month was determined by
the observation of the new moon. The number of months in the year was
usually twelve
(1 Kings 4:7; 1 Chronicles 27:1-15) but every third year an
additional month (ve-Adar) was inserted, so as to make the months
coincide with the seasons. "The Hebrews and Phoenicians had no word
for month save 'moon,' and only saved their calendar from becoming
vague like that of the Moslems by the interpolation of an additional
month. There is no evidence at all that they ever used a true solar
year such as the Egyptians possessed. The latter had twelve months of
thirty days and five epagomenac or odd days.", Palestine Quarterly,
January 1889