The Limerick Calendar is a solar calendar created by me in year 2023 of the Gregorian Calendar. It uses 5 day weeks and 12 months. The first 11 months are each 6 weeks (30 days total) long and the 12th month is 7 weeks (35 days total) long.
The beginning of the Limerick Calendar year is meant to align with the Spring Equinox in the Northern Hemisphere (Autumnal Equinox in the Southern Hemisphere). The first day of year 1 on the Limerick Calendar is the same as March 21st, 1972 on the Gregorian Calendar.
Every few years, an extra day is added to the Limerick Calendar year, making the year 366 days long instead of 365 days long. These years are called "leap years".
A limerick is a poem that consists of 5 lines. An example of a limerick is shown below:
There was an Old Man with a beard,
Who said, "It is just as I feared!
Two Owls and a Hen,
Four Larks and a Wren,
Have all built their nests in my beard!"
- Edward Lear
Just as limericks have 5 lines, the Limerick Calendar has 5 days in a week.
To adjust for the misalignment of the rotation of the Earth compared to the length of a tropical year (the amount of time the Earth takes to revolve around the Sun), an extra day called a "leap day" is added after the 7th week of the 12th month of all Limerick Calendar years that are divisible by 4 but not divisible by 128. These years are called "leap years".
To keep the days of the week stable and consistent, a leap day is not considered to be a day of the week. Whether a leap day is added to a Limerick Calendar year or not, the first day of every Limerick Calendar month is always the first day of the week. This is in opposition of the Gregorian Calendar, where the day of the week of the first day of every month shifts from year to year and from month to month.
The reason for leap years is the same as the Gregorian Calendar. The Earth revolves around the Sun on average in about 365.2421891 days (365 days, 5 hours, 48 minutes, and 45.138 seconds), so after about 4 years the Earth will have rotated on its own axis about 1 extra time, meaning an extra day will have happened compared to if the Earth revolved around the Sun every exactly 365 days.
The Gregorian Calendar issues a leap year every 4 years with a few caveats. Every 100th year (years ending divisible by 100 in AD/CE) except for every 400th year (years divisible by 400 in AD/CE) is not a leap year. For example, year 1996 in the Gregorian Calendar is a leap year, as are 2000 and 2400, but 2100, 2200, and 2300 are not leap years. The average length of a Gregorian Calendar year is 365.2425 days, which means the Gregorian Calendar drifts away from the average tropical year by 1 day about every 3217 years.
The average length of a Limerick Calendar year is 365.2421875 days, which is much closer to the average tropical year length. The Limerick Calendar drifts away from the average tropical year by 1 day about every 625000 years.
Limerick Calendar Alignment With the Gregorian Calendar
Year 1 of the Limerick Calendar starts on the same day as March 21st, 1972 of the Gregorian Calendar. The reason for this is so the first day of the year on the Limerick Calendar will be March 21st of the Gregorian Calendar up through year 2199 of the Gregorian Calendar. Year 2100 of the Gregorian Calendar is not a leap year and year 128 of the Limerick Calendar is not a leap year. To keep the leap years aligned from the creation of the Limerick Calendar to as far into the future as possible, a point was made to make sure February 28th, 2100 of the Gregorian Calendar occurred in year 128 of the Limerick Calendar.
Date Syntax (Normal)
The following syntaxes are used for writing Limerick Calendar dates:
- [year] month:day
- [year] day_of_year
For example, day 17 of month 10 of year 28 in the Limerick Calendar (January 1st, 2000 in the Gregorian Calendar) is written as  10:17 in the [year] month:day syntax or  287 in the [year] day_of_year syntax
Limerick Calendar years can be positive, negative, or 0. The day before  1:1 is  12:35 and the day before  1:1 is [-1] 12:35.
Date Syntax (Playing Card)
The day of the year can be represented using French-suited (Ace, 2 through 10, Jack, Queen, King, all of which of Clubs, Hearts, Spades, and Diamonds, along with 2 Jokers) playing cards, although representing a date using playing cards will only state which day of the year a Limerick calendar date is and not the year.
Most poker decks of French-suited playing cards come with 52 playing cards with values and 2 Jokers. There are a few quirks of these 52 playing cards plus 2 joker cards that match a solar calendar year well:
- 4 suits (Clubs, Hearts, Spades, Diamonds) vs 4 seasons (Clubs = Spring, Hearts = Summer, Spades = Autumn, Diamonds = Winter)
- Adding all the number values of cards (Ace = 1, 2 = 2, ..., Jack = 11, Queen = 12, King = 13) results in 364. Add a Joker (Joker = 1) to get 365 days (nonleap year) and add the second Joker to get 366 days (leap year).
Any date in the Limerick Calendar can be represented uniquely with only 2 French-suited playing cards. It is possible to represent the Northern and Southern Hemispheres with the playing card syntax with a distinct "left" and "right" side pile. To remove ambiguity and allow both hemispheres to be represented, both hemispheres use a slightly different system.
Before explaining the playing card syntax, I'm going to try and explain the logic used for it. As I am from the Northern Hemisphere, I will explain the Northern Hemisphere version first and then explain the differences of the Southern Hemisphere version to the Northern Hemisphere version.
Logic for Playing Card date syntax (Northern Hemisphere)
A full suit (Ace through King) adds up to 91 and there are 90 days in each season, excluding the 4th season. To get 90, you can add King through 2 (13 + 12 + ... + 2). Counting from 1 through 13 can be done by doing the following:
- 1 = Set Ace on right side pack
- 2 = Set 2 on right side pack on top of Ace
- 3 = Set 3 on right side pack on top of 2
- 4 = Set 4 on right side pack on top of 3
- 11 = Set Jack on right side pack on top of 10
- 12 = Set Queen on right side pack on top of Jack
- 13 = Set King on right side pack on top of Queen
Now every card of the suit is on the right side pack, but we're not at 90 yet.
- 14 = Set King from right side onto left side pack. Take all cards from right side pack. Set Ace on right side pack. ([King] + Ace = 14)
- 15 = Set 2 on right side pack on top of Ace ([King] + 2 = 15)
- 16 = Set 3 on right side pack on top of 2 ([King] + 3 = 16)
- 17 = Set 4 on right side pack on top of 3 ([King] + 4 = 17)
- 23 = Set 10 on right side pack on top of 9 ([King] + 10 = 23)
- 24 = Set Jack on right side pack on top of 10 ([King] + Jack = 24)
- 25 = Set Queen on right side pack on top of Jack ([King] + Queen = 25)
Now every card of the suit is on the right + left side packs, but we're still not to 90 yet.
- 26 = Set Queen from right side pack onto left side pack. Take all cards from right side pack. Set Ace on right side pack. ([King + Queen] + Ace = 26)
- 27 = Set 2 on right side pack on top of Ace ([King + Queen] + 2 = 27)
- 36 = Set Jack on right side pack on top of 10 ([King + Queen] + Jack = 36)
Repeat this general pattern until the top card of the left side is 3 and the top card of the right side is 2. This is 90, the last day of a 90 day season.
On the day after the 90 day season is done, do the following to set up for this day:
- Set the 2 from right side pack onto left side pack
- Set the Ace from right side pack away from left and right side packs
This signifies that the 90 days of the season are done.
The season suits, in order, are "Clubs", "Hearts", "Spades", and then "Diamonds". Days 1 through 90 (1:1 through 3:30) use the Clubs suit, 91 through 180 (4:1 through 6:30) use the Hearts suit, 181 through 270 (7:1 through 9:30) use the Spades suit, and 271 through 360 (10:1 through 12:30) use the Diamonds suit.
Repeat the 90 day pattern for all 4 suits.
- Day 91 (4:1) will have 2 of Clubs on top of left side pack and Ace of Hearts on right side pack
- Day 181 (7:1) will have 2 of Hearts on top of left side pack and Ace of Spades on right side pack
- Day 271 (10:1) will have 2 of Spades on top of left side pack and Ace of Diamonds on right side pack
- Day 361 (12:31) will have 2 of Diamonds on top of left side pack
Days 361 through 365 (or 366) are the last 5 (or 6) days of the year and are treated differently from the previous 360 days, as follows:
- On day 361 (12:31), set Ace of Clubs on right side pack.
- On day 362 (12:32), set Ace from right side pack onto left side pack. Set Ace of Hearts on right side pack.
- On day 363 (12:33), set Ace from right side pack onto left side pack. Set Ace of Hearts on right side pack.
- On day 364 (12:34), set Ace from right side pack onto left side pack. Set Ace of Diamonds on right side pack.
- On day 365 (12:35), set Ace from right side pack onto left side pack. Set Joker on right side pack.
- On day 366 (12:36 [leap year]), set Joker from right side pack onto left side pack. Set second Joker on right side pack.
At the start of the year (1:1), do the following to set up for this new year:
- On day 1 of the new year (1:1), set Joker from right side pack onto left side pack before
When a year is finished, the order of the year on the left side pack from bottom to top will be the following (K = King, Q = Queen, J = Jack, A = Ace, F = Joker [Fool], C = Clubs, H = Hearts, S = Spades, D = Diamonds):
- KC-2C, KH-2H, KS-2S, KD-2D, AC, AH, AS, AD, F (53 cards) on a year that is non-leap year
- KC-2C, KH-2H, KS-2S, KD-2D, AC, AH, AS, AD, F, F (54 cards) on a leap year
A Joker will be the top card on the left side pack for the first 13 days of the year (1:1 through 1:13), as it is the last card of the previous year.
Example Limerick Calendar dates in normal and playing card (Northern Hemisphere) syntaxes
Some example dates are as follows (K = King, Q = Queen, J = Jack, A = Ace, F = Joker [Fool], C = Clubs, H = Hearts, S = Spades, D = Diamonds):
- 1:1 = F AC
- 1:2 = F 2C
- 1:13 = F KC
- 1:14 = KC AC
- 1:15 = KC 2C
- 1:25 = KC QC
- 1:26 = QC AC
- 1:27 = QC 2C
- 1:36 = QC JC
- 1:37 = JC AC
- 3:30 = 3C 2C
- 4:1 = 2C AH
- 4:13 = 2C KH
- 4:14 = KH AH
- 6:30 = 3H 2H
- 7:1 = 2H AS
- 9:30 = 3S 2S
- 10:1 = 2S AD
- 12:30 = 3D 2D
- 12:31 = 2D AC
- 12:32 = AC AH
- 12:33 = AH AS
- 12:34 = AS AD
- 12:35 = AD F
- 12:36 = F F
Logic for Playing Card date syntax (Southern Hemisphere)
The Southern Hemisphere version of the Playing Card date syntax is the same as the Northern Hemisphere version with the following exceptions:
- Instead of the suit order being "Clubs, Hearts, Spades, Diamonds", the suit order is "Spades, Diamonds, Clubs, Hearts" in order to align to the correct season suit
- All instances of left and right side piles are swapped
Example Limerick Calendar dates in normal and playing card (Southern Hemisphere) syntaxes
Some example dates are as follows (K = King, Q = Queen, J = Jack, A = Ace, F = Joker [Fool], S = Spades, D = Diamonds, C = Clubs, H = Hearts):
- 1:1 = AS F
- 1:2 = 2S F
- 1:13 = KS F
- 1:14 = AS KS
- 1:15 = 2S KS
- 1:25 = QS KS
- 1:26 = AS QC
- 1:27 = 2S QC
- 1:36 = JS QC
- 1:37 = AS JC
- 3:30 = 2S 3C
- 4:1 = AD 2C
- 4:13 = KD 2C
- 4:14 = AD KD
- 6:30 = 2D 3D
- 7:1 = AC 2D
- 9:30 = 2C 3C
- 10:1 = AH 2C
- 12:30 = 2H 3H
- 12:31 = AS 2H
- 12:32 = AD AS
- 12:33 = AC AD
- 12:34 = AH AC
- 12:35 = F AH
- 12:36 = F F
Related Calendar Systems
Another 5 day week calendar system is the Paratheo-Anametamystikhood of Eris Esoteric (POEE) Calendar, which is described on page 00034 of the "Principia Discordia".