Synodic Months to Weeks (mo (syn) to wk)
1 synodic month equals 4.218655714 weeks (rounded).
How to convert synodic months to weeks
To convert synodic months to weeks, multiply the number of synodic months by 4.218655714. The factor is rounded to 10 significant digits. To go the other way, multiply weeks by 0.2370423347 (rounded).
weeks = synodic months × 4.218655714
Example: 10 synodic months = 42.18655714 weeks.
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))
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
Week (wk)
Seven days. The seven-day week comes from the ancient Near East and is nearly universal in the modern calendar.
Nothing in the sky produces a seven-day cycle, which makes the week a human invention with a contested pedigree. Babylonians marked the 7th, 14th, 21st and 28th of the lunar month as special, but that was not a continuous cycle. A continuous seven-day cycle tied to the Sabbath is attested in Judaism by the 6th century BC at the latest, and scholars disagree on whether it was borrowed from Babylon or developed independently. The Romans later used a week named for the Sun, the Moon and the five visible planets, and in AD 321 Emperor Constantine decreed it across the empire.
A week is seven days, or 604,800 seconds, and it divides evenly into neither months nor years, which is why calendars shift against it. The ISO 8601 standard starts each week on Monday and assigns week 1 to the week containing the year's first Thursday, so some years have a week 53. Other societies used different lengths: Rome had an eight-day market cycle, and revolutionary France used a ten-day week from 1793 to 1802. The English word comes from Old English wice, meaning a turn or succession.
1 week = 604,800 seconds (exactly).
Sources: Wikipedia: Week; Wikipedia: ISO week date
Related conversions
- Weeks to synodic months (reverse)
- Synodic months to seconds
- Synodic months to minutes
- Synodic months to hours
- Synodic months to days
- Synodic months to months
- Synodic months to years
- Seconds to weeks
- Minutes to weeks
- Hours to weeks
- Days to weeks
- Months to weeks
- Years to weeks
- Milliseconds to weeks
- Microseconds to weeks
- Nanoseconds to weeks
- Decades to weeks
- Centuries to weeks
- Millennia to weeks
See all time units.