Lunar month

In lunar calendars, a lunar month is the time between two successive similar syzygys (new moons or full moons). There are many variations. In Middle-Eastern and European traditions, the month starts when the young crescent Moon becomes first visible at evening after conjunction with the Sun 1 or 2 days before that evening (e.g. in the islamic calendar). Others use a reckoned Moon (e.g. the Hebrew calendar), or use a tabular scheme (Gregorian calendar). Yet others have months run from Full Moon to Full Moon. Calendars count integer days, so months may be 29 or 30 days in length, in some regular or irregular sequence. But all lunar month approximate the mean length of the synodic month of approximately 29.53059 days (29 days, 12 hours, 44 minutes and 3 seconds).