Lunar month with the Sun one or two days before that evening ("e.g.", in the Islamic calendar). In ancient Egypt the lunar month began on the day when the waning moon could no longer be seen just before sunrise. Others use calculation, of varying degrees of sophistication, "e.g.", the Hebrew calendar or the ecclesiastical lunar calendar. Yet others 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. In India the month from conjunction to conjunction is divided into thirty parts known as "tithis". The
Lunar month month because it is the cycle of the visible phases of the Moon. Most of the following types of lunar month, except the distinction between the sidereal and tropical months, were first recognized in Babylonian lunar astronomy. The period of the Moon's orbit as defined with respect to the celestial sphere of apparently fixed stars (nowadays the International Celestial Reference Frame (ICRF)) is known as a sidereal month because it is the time it takes the Moon to return to a similar position among the stars (): days (27 d 7 h 43 min 11.6 s). This type of month