#Tropicalyear = 365.242190 #days (end 20th cen)
#Earth's axial tilt returns to same angle with respect to the #sun
Jewish calendar aligns tropical #year & lunar #7months over 19-year cycle with years that range from 353 to 385 days.
AM5785 will be a standard 354 days.
#RoshHashanah #timekeeping #analemma #astronomy
Analemma courtsey J. Fishburn (CC-BY-SA 3.0)
Google's cute doodle for the Leap Day (29th February) 2024.
WHAT IS A LEAP DAY/YEAR?🤔🧐
Common/Calendar Year (y)=365 solar days 🗓
Solar/Tropical/Astronomical Year (Y)=365.2425 solar days🌏🌞
Y-y=0.2425; 4*(Y-y)=0.97=1-0.03 (+1 if divisible by 4)
100*(Y-y)=24.25=(25-1)+0.25 (again -1 if divisible by 100)
400*(Y-y)=97=4*(25-1)+1 (again +1 if divisible by 400)
That is to say,
Using logical and modulo operators, the year n is said to be a leap year if and only if:
(n mod 4=0)∧((n mod 100≠0)∨(n mod 400=0)).
In other words, a year is a leap year if it is evenly divisibly 4, except for years that are evenly divisible by 100 but not evenly divisible by 400.
For example, 2024 and 2028 are leap years; 2100 and 2200 are not, but 2400 and 2800 are.
This is our clever method to ensure that our calendar stays aligned with our seasons or Earth's orbit over time. If nothing were done about this discrepancy, our calendar would slowly drift out of sync with the Earth's orbit and seasons. After 100 years, we would be off by about 25 days! So, to fix this, we add an extra day, February 29, to the calendar every four years, with the exception that a year evenly divisible by 100 is not a leap year unless it is also evenly divisible by 400 (as shown in the calculations).
#LeapDay #LeapYear #Feb29 #February29 #29Feb #29February #ExtraDay #February #Earth #Sun #SolarYear #SolarDay #Astronomy #Calendar #CommonYear #CalendarYear #TropicalYear #AstronomicalYear #Season #Seasons #EarthOrbit #OrbitEarth #Year #Discrepancy #Discrepancies #Synchronization
The Temple of the Cross Sanctuary Text at Palenque contains a well known series of mythological dates within the west panel that are spatially and thematically distinguished from the historical dates found in the east panel. The mythological text in
In 1900, Maksim Trpković revised the #JulianCalendar. Under his system, an year that yields a remainder of 0 or 400 when divided by 900 is a #LeapYear.
Milutin Milanković slightly altered this in 1923, changing the rule to years that give a remainder of 200 or 600. A mean year in this calendar is just 2 seconds off the #TropicalYear. It is used by some, but not all, #EasternOrthodox churches.
The Gregorian calendar came into force in 1568 and was promptly adopted in #Catholic countries. #Protestant and #Orthodox countries were slower, since they didn't want to use a #calendar invented by Catholics.
In 1568, 10 days were skippedin #October to recalibrate the civil calendar with the #TropicalYear. By the time #Britain gave in and adpted the Gregorian calendar in 1758, they had to sip 11 days.
But, as we now know, the #JulianCalendar's mean year is about 11 minutes 15 seconds longer than the #TropicalYear, and by the 4th century AD, the dates of the #solstices and #equinoxes had drifted from their official dates by several days.
In the 16th century, #Pope Gregory XIII used his authority as #PontifexMaximus to reform the calendar again, because that is something #popes can do.
This means that the Romans had no real concept of, say, "The 28th of Martius"; they thought of that day as "three days before the kalends of Aprilis".
But there was another issue. Even with 12 months, the normal #calendar year was a little shorter than the #TropicalYear. No problem, right? Just add an extra month every 2-3 years, like basically every other culture does?
Yeah, the Romans were *the worst* at timekeeping.
Jennifer Lynn Bartlett moved
Pustam | पुस्तम | পুস্তম🇳🇵
Azimech
Infrapink (he/his/him)