Please Explain: Calendars

Friday, December 07, 2012

The Mayan calendar ends on December 21, 2012, prompting some to believe the world will end on that date. For this week’s Please Explain, we thought we’d find out about that calendar and the many others used through history by different cultures to account for the days and months that make up the year. Joining us are John Pratt and Ken Seidelmann, Research Professor at the University of Virginia’s Department of Astronomy.


John Pratt and Ken Seidelmann

Comments [17]

Ursula from Brooklyn

I tweet the date according to the French Revolutionary Calendar every day at For example, today is the 17th of Frimaire -- Cypress Tree day -- in the 221st year of the French Era. I have also written a very basic essay about the calendar here:

Dec. 07 2012 02:43 PM
Amy from Manhattan

I think I read a long time ago that the 2 additional months in the Julian calendar were July & August, named for the emperors Julius & Augustus. Given what 1 of the guests said about which month was the 1st in the Roman calendar, I'm not sure if that was the middle of the year or not. I don't know how they worked a year w/10 months before then, either.

And to add to my call about Birkat ha-Chamah (Blessing of the Sun), the every-28-years Jewish holiday, the book I have about it points out that the Hebrew calendar is accurate to within 1 day in 14,000 years based on lunar months & 6 minutes, 40 seconds a year in reconciling the lunar calendar & the solar year. This would lead to the holydays' coming out in the wrong season after thousand & thousands of years. The book then goes on to say that this will be rectified by the coming of the Redemption & the reestablishment of the Sanhedrin....

Dec. 07 2012 02:13 PM
Norooz from Long Island

-Persian calendar is followed by at least 150 million people in Iran, Afghanistan and Tajikistan , it is based on Zoroastrian religion and it starts at the first of the spring "Norooz" I would suggest you to have a program about Norooz and Persian calender.

-January first is not arbitrary it is in the middle of catholic and orthodox christmas

Dec. 07 2012 02:00 PM
Cynthia from NYC

Yup the ecclesiastical year in the Orthodox Church starts on Sept 1st. Easter in the Othodox church is calculated 1st sunday after the first full moon after the equinox after Passover.

Dec. 07 2012 01:58 PM
Sheldon from Brooklyn

I thought that the Russians switched over in the early 20th century. Even though, they still celebrate Christmas on an orthodox calender.

Dec. 07 2012 01:56 PM

What is the relationship between numbers and measurement of time in calendars? E.g. in our calendar the measurement of time is based on 60 (seconds, minutes), 24 (hours per day) 7 (days per week) 30/21 (days per month) 12 (months per year)
Are these number considered sacred in our culture and more important than astronomical events,such as lunar month?
In the Siddhanta theory measurement of time was based on human breath (prana). Is there any calendar based on these measurements?

Dec. 07 2012 01:45 PM
Bill from UES

Doesn't anybody pre-screen the guests? These two are a bore and the segment is a snore...zzz...

Dec. 07 2012 01:44 PM
Mike from Inwood

Midnight is not arbitrary; it is half way between two noons. Noon is the time when the sun is directly overhead.

Dec. 07 2012 01:37 PM

Penelope from Astoria
In Western Christianity, using the Gregorian calendar, Easter always falls on a Sunday between 22 March and 25 April, inclusively.
Eastern Christianity bases its calculations on the Julian Calendar. Due to the 13-day difference between the calendars between 1900 and 2099, 21 March corresponds, during the 21st century, to 3 April in the Gregorian Calendar. Easter therefore varies between 4 April and 8 May on the Gregorian calendar

Dec. 07 2012 01:37 PM
Sheldon from Brooklyn

It's a shame the [Oct]ober [Nov]ember, and [Dec]ember are misaligned because a few Romans wanted to stuff a couple of months in the middle of the year.

Dec. 07 2012 01:36 PM

Quakers will still use "First Day" "Second Day" etc. at times...

Dec. 07 2012 01:31 PM

to correct your guest
Evidence of continuous use of a seven-day week appears with the Jews during the Babylonian Captivity of the 6th century BC.[2] Both Judaism (based on the Creation narrative in the Bible) and ancient Babylonian religions used a seven-day week

Dec. 07 2012 01:30 PM
Matthew from New Rochelle

Off topic...but I'm still laughing from yesterday when Philip Galanes was on and Susan from Brooklyn called...Wahahaha! She rocks, it made my day. <3 WNYC and its listeners~

P.S. Leonard, maybe consider having her fill in for you next time you're away ;-)

Dec. 07 2012 01:29 PM

How would the world be different if we followed a calendar that is not solar or I guess Christian? What uf we were following the Jewish, Hindu calendars

Dec. 07 2012 01:27 PM
Tom Moore from brooklyn

when it comes to calendars - you should ask about pope benedict saying in his new book - that Christmas is really off by a few years... maybe they're comment on that...

Dec. 07 2012 01:26 PM
Penelope from Astoria

How is the Catholic Easter figured out verses the Greek Orthodox Easter? Also, are either of these holidays connected to how the Jews calculate the date of Passover?

Dec. 07 2012 12:53 PM
John A from Westchester

Was the older way of 'suffixing' dates, just phased out: B.C. and A.D. - was it used since the beginning or was it adopted more recently than 2,000 years ago?

Dec. 07 2012 11:22 AM

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