Synodic Months to Months (mo (syn) to mo)

1 synodic month equals 0.9702241114 months (rounded).

1 synodic month = 0.9702241114 months

How to convert synodic months to months

To convert synodic months to months, multiply the number of synodic months by 0.9702241114. The factor is rounded to 10 significant digits. To go the other way, multiply months by 1.030689702 (rounded).

months = synodic months × 0.9702241114

Example: 10 synodic months = 9.702241114 months.

Months and years are not constant. This site uses the average Gregorian year of 365.2425 days, so one 'year' converts to 365.2425 days, not 365; use 'common year' for exactly 365 days.

Approximate value. Standards for the synodic month varied by place and period, so this converter uses the most commonly cited value. Treat results as estimates, not exact figures.

About these units

Synodic Month (mo (syn))

AstronomicalCurrent unitApproximate value

About 29.53 days, the time from one new moon to the next. The basis of lunar and many religious calendars.

A synodic month is the span from one new moon to the next, when the Moon returns to the same position relative to the Sun as seen from Earth. Its mean length is about 29.53 days, or 29 days 12 hours 44 minutes 3 seconds. The word synodic derives from a Greek term for meeting, since the Sun and Moon meet in the sky at each new moon.

Individual months are far from equal. Because the Moon's orbit is elliptical and the Sun perturbs it, a single lunation can run from about 29.27 to about 29.83 days, and in a given year the interval can differ from the mean by up to roughly seven hours. In 2001, for instance, lunations ranged from 29 days 19 hours in January to 29 days 7 hours in July.

Babylonian astronomers were the first to recognise this kind of month and to work out its mean length, and the quantity still underlies lunar and lunisolar calendars such as the Islamic, Hebrew and Chinese ones. It is longer than the sidereal month of about 27.3 days because Earth moves along its orbit while the Moon circles it.

1 synodic month = 2,551,442.976 seconds (approximately).

Sources: Wikipedia: Lunar month

Month (mo)

CalendarCurrent unit

One twelfth of an average Gregorian year: 30.436875 days. Calendar months actually range from 28 to 31 days.

Month and Moon are cognates, and the unit began as the Moon's cycle of phases, about 29.53 days from one new moon to the next. The trouble is that 12 of these fall short of a solar year, so calendars have had to choose. The Islamic calendar stays purely lunar, so its year is about 11 days shorter than the solar year, while the Hebrew calendar is lunisolar, using a 19-year cycle with an extra month. Even the start of a lunar month is still debated between observing the crescent and calculating it.

Gregorian months are a compromise that drifted far from the Moon. Their lengths run from 28 to 31 days, and this site uses their mean of 30.436875 days, one twelfth of the average year. The names also keep Roman history: September to December preserve the Latin numerals for seven to ten, since they were originally the seventh to tenth months, and Quintilis and Sextilis were renamed for Julius Caesar and Augustus. When a contract says month, check whether it means a calendar month or thirty days.

1 month = 2,629,746 seconds (exactly).

Sources: Wikipedia: Month; Wikipedia: Lunar calendar

Related conversions

See all time units.