The Moon rotates around the earth 13 times in our 12 month year. That is ever 27.322 days. 365.25 days to go around the sun. If you do the math, 365.25 divided by 27.322 equals 13.36 months! Instead of the 12 months we have now.
tentofield
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The lunar month is 29.53 days. If you have 13 lunar months that gives you 383.89 days in the year. If you have 12 lunar months you get 354.36 days. Consequently if you want to divide the year into lunar months you get 12 months plus a 12 day unnamed period or, you can add a day or two to each month to fill the year with 12 months. And that is what has been done.
Funloving
the 365.25 wouldn't change, so the dates of solstices etc wouldn't change either. different than now, but just curious if anyone has an explanation as to why the people who set up this calendar didn't use a 13.36 calendar. where a few (4)months like now would have an extra day. Each month would coordinate with the moon. Every woman's monthly cycle would be easier to track if they were off cycle.
quantumclaustrophobe
Julius Caesar's astronomers explained the need for 12 months in a year and the addition of a leap year to synchronize with the seasons. At the time, there were only ten months in the calendar while there are just over 12 lunar cycles in a year.
The months of January and February were added to the calendar and the original fifth and sixth months were renamed July and August in honour of Julius Caesar and his successor Augustus.
These months were both given 31 days to reflect their importance, having been named after Roman leaders.
?
the lunar month has a mean period of 29.53059 days, and a circle has 360 degrees. So if you round off the lunar cycle to 30 days and divide it into 360 degrees, you come up with 12 months.
The 0.47 day round of error for each month, times the 12 months, accumulates to give us the other 5 1/2 days in a year, or 365 1/2 days.
poornakumar b
"Because we use a solar calendar, not a lunar one" (as someone said above) is just parroting. Then why the hell we have months too? And like de Saade cut the month's feet to fit the year as its cot? Ridiculous.
In India Lunar Calender is followed in two ways: one is sidereal month, but it is not termed a month; rather it is observed as Lunar transit through the 27 Asterisms one a day(Nakshatras; or Lunar Mansions as per Chinese).
The synodal month between two successive FullMoons or NewMoons (or any of the 30 phases) is called the month. I think you should consider this. It falls short of a year by 11 days. Then, every three years when the stagger in the Nakshatras goes skewed an extra month is introduced like extra January when the FullMoon returns to the assigned Nakshatra, But then it gets in excess to make up thirty days after 10 years. Then a regular month just gets wiped out as emptied month. It is all complicated.
The Indians follow Lunar Calender for routine work but correct to bring it on par with Solar Year without breaking the rhythm of Lunar phases. Solar event for instance, like entry into a new Zodiacal sign (=Sankranthi) is noted & some of them like Makar Sankranthi (entering Capricorn; then considered as Winter Solstice, which now has moved to Sagittarius). Similarily Maesha Sankranthi (to Aries) that was Spring Equinox then is celebrated as New Year in some parts of India.
If you want Calender reform to fit month too, there are enough number of models already to choose from. But can you (or those) educate yourself?