Thirteen months of sunshine

Twelve months of thirty days, a thirteenth of five or six, and a year number that trails ours by seven or eight. The Ethiopian calendar — still running on a leap rule Julius Caesar would recognize. ← Calendar Contraptions

Ethiopia's tourist board has long advertised thirteen months of sunshine. It is not quite a boast: the thirteenth month has five days most years and six every fourth year, so the "extra sunshine" is six days at best, and every fourth year at that. But the brochure is honest about the machinery. The Ethiopian calendar kept the old Egyptian skeleton — twelve months of thirty days and a stub of year-end days — and never adopted the Gregorian fix that skips three leap days every four centuries. Its year number runs on a rival Christmas count, seven or eight years behind the one Europe uses. And its leap years are named after the four Evangelists.

Pick a date. The machine reads it back the way an Ethiopian calendar page would — and in the Egyptian calendar it grew from.

The seven-year difference

The Ethiopian year number is not one number. From January until the new year it runs eight behind the Gregorian count; from 1 Mäskäräm onward, seven. The flip happens every September — watch it below for the picked year. The essay "Eight years, then seven" explains whose arithmetic is behind each count.

The year's thirteen months

Twelve months of thirty days, then Pagume — the little month that holds whatever is left. The colors mark the three Egyptian seasons the months still walk through: the flood, the growth, the harvest. The gold chip is the year's one irregular month.

Where the brochure rule dies

The easy rule everyone knows: New Year is 11 September — 12 September in the years right after a leap year. It holds for one double century, because the Ethiopian leap rule never skips while the Gregorian skips three century years in four. The table walks 1 Mäskäräm across a range of years so you can watch the rule hold, then bend.

Fixed dates

The festivals that sit on fixed Ethiopian dates, read in both calendars. Easter is the exception — Fasika moves with the moon, computed by the same reckoning as the Eastern churches; the Easter piece takes that machine apart.

The numerals

Geʽez writes numbers with letters, borrowed from the Greek: nine units, nine tens, a hundred-mark, a ten-thousands mark. Two-digit groups stack left to right, each followed by its multiplier. The reading below is the picked date in that system, with the decomposition spelled out.

Ethiopian → Gregorian

Eight years, then seven

Around AD 400 the Alexandrian monk Annianus fixed the Incarnation — the Annunciation — at 25 March of what he counted as AD 9, and started his civil year seven months earlier, on 29 August AD 8. That is the Ethiopian epoch: 1 Mäskäräm of year 1, our 29 August AD 8 on the Julian calendar. In AD 525, Dionysius Exiguus, building his own Easter tables, placed the Incarnation nine years earlier than Annianus had. Europe eventually followed Dionysius; Ethiopia kept Annianus. The gap between the two year counts is therefore eight years — and because Annianus began his year in late summer, the gap shrinks to seven the day the Ethiopian new year passes. That flip is the machine above.

The Coptic church counts the same days from a different zero: the accession of Diocletian in AD 284, whose persecution of Christians gave the era its name — the Era of the Martyrs. Its years trail the Ethiopian count by exactly 276, the distance between 29 August AD 8 and 29 August AD 284. The Ethiopian article of the same machine quotes the old Easter-cycle arithmetic: Dionysius added 15 nineteen-year cycles to the 13 already run under Diocletian's era — 15 × 19 + 13 × 19 = 532, the great Easter cycle the Easter piece visits.

The clock that never skips

Every fourth Ethiopian year has a sixth day in Pagume. No exceptions: no century rule, no 400-year correction, no skipped leap days. That is the Julian rule, and the Ethiopian calendar has kept it without interruption since the reformed Egyptian calendar was set running — the sixth day lands at the year's end, always on 29 August of the Julian calendar, so the two calendars keep step forever. The Gregorian reform of 1582, which drops three leap days every four centuries to stay tied to the equinox, never reached this clock.

The consequence is a slow, orderly disagreement. From March 1900 to February 2100 the Ethiopian new year lands on our 11 September — except in the year right after a leap year, when it lands on the 12th. (Those two claims are the same claim: an Ethiopian year with 366 days pushes its successor one day later in every calendar.) In 1900 and 2100 the Gregorian rule skips a leap day the Ethiopian clock does not, and the tidy correspondence breaks. After February 2100 the new year drifts to the 12th and, over the following centuries, keeps sliding — the table above walks you to the edge.

The Evangelist wheel

The four-year leap cycle has names. The year after a leap year is the year of John, then come Matthew and Mark, and the leap year itself — the one with six days in Pagume — belongs to Luke. The wheel turns once every four years and never meets an exception: after twenty centuries the pattern is exactly as regular as the day it encodes. Pick any year in the table above and the note column will tell you whose year it is; the machine's year row always names the current one.

Egypt in the highlands

The Ethiopian calendar and the Coptic calendar are the same machine with two faceplates. Both run twelve 30-day months plus a little month; both start the year on the same days; both keep the Julian leap rule. They differ in era (Ethiopia counts from the Incarnation, Egypt from Diocletian — 276 years apart) and in what they call things. The month names in Egypt are the old Egyptian ones through Coptic: Thout for Thoth, god of wisdom and science; Hathor the goddess; Paremhat for the festival of Amenhotep; Parmouti for the harvest goddess Renenutet; Pashons for Khonsu. The little month is Pi Kogi Enavot, Bohairic for "the little month"; the Sahidic church called it by the Greek word for the days "brought in" — the epagomenal days.

The Coptic calendar is older than either church's use of it: it is the ancient Egyptian civil year reformed on the Decree of Canopus (238 BC, one extra day every fourth year), which only took hold when Augustus made it Egypt's official calendar. Its three seasons — the inundation (Akhet), the growth (Peret), the harvest (Shomu), four months each — are still commemorated by special prayers in the Coptic liturgy, and Egyptian farmers still use the months to track the agricultural year. Egypt ran its fiscal year on this calendar until the Gregorian reform arrived on 11 September 1875 — which was, of course, 1 Thout 1592 A.M. Its Christmas sits on 29 Koiak — in this era 25 December Julian and 7 January Gregorian — the same day as the Ethiopian Genna on 29 Taḫśaś.

Numbers borrowed from Greece

The Geʽez script writes numbers with letters, in a system borrowed from the Greek — possibly by way of Coptic uncial letters. Like Greek numerals it has no zero and no place value: nine unit signs, nine tens signs, a hundreds sign (፻), and a ten-thousands sign (፼). Two-digit groups stack left to right, each followed by its multiplier's sign — the system is "reduced" compared to Greek in that it has no signs for the multiples of 100 themselves. On a coin of Menelik II, the year 1889 is written ፲፰፻፹፱ — eighteen, hundred, eighty, nine. The same rule spells 475 as ፬፻፸፭ (four, hundred, seventy, five) and 83,692 as ፰፼፴፮፻፺፪ (eight, ten-thousands, thirty, six, hundred, ninety, two). Historically the signs were Greek letters marked with a vinculum, an over- and underline; the Ethiopic forms kept the habit but changed the letters.

Honest limits

These are plain calendar dates — no time zones, no sunset conventions, no pretending. The arithmetic is exact for every proleptic date; the names are another matter. Amharic, Tigrinya and Geʽez speakers spell and pronounce the month names differently, and this page transliterates one common scheme. The church's movable feasts — Easter above all — are computed the way the Eastern churches compute them, and its fasting seasons fill another yearbook again; this page shows the fixed dates and points at the Easter piece for the movable machine. And a small honest quirk: if your birthday falls on the sixth day of Pagume, it comes around once every four years — a rarer treat than February 29.