Gregorian To Thellid Date Conversion

Put a Gregorian date in, get the Thellid out! Magic!

Enter the Gregorian day, month and year in numeric form. The year must have 4 digits.

Day of the Month: Month: Year:

Converting Gregorian To Thellid Dates

The Thellid Calendar begins the year on the day following the Greenwich Winter Solstice, but this solstice in today's Gregorian Calendar occurs on the 21st or 22 second of December, ie 9 or 10 days before the Gregorian year end on the 31st, so the Thellid year begins 9 or 10 days earlier than the Gregorian year.

To complicate matters further, there have been times in the past where the solstice in question occurred MORE that 10 days from Old Year's Day, even as far as 19 days in the 16th century when Pope Gregory decided to do something about it. Be aware that there is considerable variation in this gap, especially in the middle ages.

In order to convert from conventional dates to Thellid dates you must:

Ascertain the date of the Greenwich Winter Solstice on the Gregorian year in question¹.
If date is LATER than the GWS then the gap between the two is the Thellid Year Day ON THE FOLLOWING YEAR. Note, this happens on all Christmas Days.
If the date IS the GWS then it is Old Year's Day in that year.
If the date falls BEFORE the GWS then:
Ascertain the Gap between the GWS and the 31st of December on the Gregorian year before.
Calculate the Gregorian Year Day in question, (check whether this a year of irregular dates, such as a Gregorian Leap Year or other adjustment.).
Add the Gap to the Gregorian Year Day to obtain the Thellid Year Day.
If the Thellid Year Day is 365 AND it is the day before the solstice, then it is a LEAP DAY!
Consult the Thellid Wall Calendar to convert the Thellid Year Day to Month, Monthday and Weekday.
Convert the year to HE.

Here are some examples to help you follow this process:

22nd of December, 1987 (death of Alice Terry):
The GWS in 1987 occurred on this date, so this was Old Year's Day!
Properly put: Old Year's Day, 11987.

25th December 2010 (Christmas Day):
The GWS in 2010 occurred on December 21, (4 days previous).
The Thellid Year Day is therefore 4 in the following year.
Properly speaking the Thellid Day is: Hithed, 4th Alvakku, 12011.

November 22, 1963 (JFK's assassination):
The GWS in 1963 occurred after this date, so there is no change of year.
The GWS in 1962 occurred on December 22, (9 days before Old Year's Day).
Nov 22 was the 326th day of 1963.
The Thellid Year Day is then 9 + 326 = 335.
Reading the Thellid Day from the wall calendar we get: Teijal, 27th Underro, 11963.

6th of June, 1944 (D-Day):
The GWS in 1944 occurred after this date, so there is no change of year.
The GWS in 1943 occurred on December 22, (9 days before Old Year's Day).
June 6 was the 158th day of 1944, (remembering that it was a Gregorian leap year).
The Thellid Year Day is then 9 + 158 = 167. The Thellid Day is: Teijal, 27th Kalvazzi, 11944.

December 22, 1903 (birth of Haldan Keffer Hartline):
The GWS in 1903 occurred on the December 23, (after this date), so there is no change of year.
The GWS in 1902 occurred on December 22, (9 days before Old Year's Day).
Dec 22 was the 356th day of 1903.
The Thellid Year Day is then 9 + 356 = 365. But the 1903 solstice was the following day, so this is a Leap Day!
Properly put: Leap Day, 11903.

You will need an ephemeris or almanac that covers the year in question. At the time of writing Time & Date provided a comprehensive table.