The month is a unit of time, used with calendars, which is
approximately as long as some natural period related to the
motion of Luna. The traditional concept arose with the cycle of
moon phases; such months are synodic months and last ~29.53
days. From excavated tally sticks, researchers have deduced that
people counted days in relation to the Moon's phases as early as
the paleolithic age. Synodic months are still the basis of many
calendars. |Table of contents| 2 Calendrical implications The
motion of the Moon in its orbit is very complicated and its
period is not constant. Moreover, many cultures (most notably
those using the Hebrew (Jewish) and Islamic calendars) start a
month with the first appearance of the thin crescent of the new
moon after sunset over the western horizon. The date and time of
this actual observation depends on the exact geographical
longitude as well as latitude, atmospheric conditions, the
visual acuity of the observers, etc. Therefore the beginning and
lengths of months in these ca