Khmer Culture & Calendar
Khmer Leap Months and Leap Days
why some Khmer years have 384 days, and how that moves the festivals
Twelve moons make only about 354 days, eleven short of a solar year. The Khmer calendar fixes this by sometimes adding one day and sometimes a whole second month of Asadh. 2026 is one of those leap-month years, and it is the reason Pchum Ben came so late this year.
Three kinds of Khmer year
- Normal year · 354 days
Twelve months that alternate between 29 and 30 days.
- Leap-day year · 355 days
Called Chantreathimeas. The month of Jesth gets 30 days instead of 29, keeping the months in step with the real moon.
- Leap-month year · 384 days
Called Athikameas. Asadh is repeated: Pathamasadh (1st Asadh) and Tutiyasadh (2nd Asadh), 30 days each, which keeps the festivals in their season.
The twelve months and their days
The bars show one Khmer lunar year. Months alternate 29 and 30 days; the gold month is the one that changes in a leap year.
Why the calendar needs leap months
A month runs from one new moon to the next, about 29½ days. Twelve of them come to about 354 days, but the sun takes about 365¼ days to bring the seasons round. Without a correction, Khmer months would drift eleven days earlier every year and, after about 16 years, Pchum Ben would fall in the hot season.
Adding a 30-day month every two or three years pulls the calendar back. Over 19 solar years the gap adds up to almost exactly seven months, because 19 solar years and 235 lunar months (19 × 12 + 7) are both about 6,940 days. In every 19-year stretch from 1990 to 2045, the calendar rules give exactly seven leap-month years.
The leap day does a smaller job. A lunar month is a little longer than 29½ days, so a 354-day year runs about a third of a day short of twelve real moons. Every few years Jesth gets a 30th day to make that up.
2026: a year with two Asadh
In 2026 the first Asadh ran from 15 June to 14 July and the second Asadh from 15 July to 13 August. The rains retreat follows the second Asadh in a leap-month year, so Chol Vassa came on 30 July 2026, nineteen days later than in 2025.
Everything after it moved too: Pchum Ben day was 22 September in 2025, 11 October in 2026, and the calendar rules give 30 September for 2027. Read more in our guide to Chol Vassa.
| Year | Leap | Chol Vassa | Pchum Ben day |
|---|---|---|---|
| 2024 | — | 21 July | 2 October |
| 2025 | Leap day | 11 July | 22 September |
| 2026 | Leap month | 30 July | 11 October |
| 2027 | — | 19 July | 30 September |
| 2028 | — | 7 July | 18 September |
| 2029 | Leap month | 26 July | 7 October |
Leap years from 2015 to 2040
| Year | Type | Extra time |
|---|---|---|
| 2015 | Leap month | 2nd Asadh: 16 July – 14 August |
| 2016 | Leap day | Jesth has 30 days (15th waning day: 4 July) |
| 2018 | Leap month | 2nd Asadh: 13 July – 11 August |
| 2020 | Leap day | Jesth has 30 days (15th waning day: 20 June) |
| 2021 | Leap month | 2nd Asadh: 10 July – 8 August |
| 2023 | Leap month | 2nd Asadh: 18 July – 16 August |
| 2025 | Leap day | Jesth has 30 days (15th waning day: 25 June) |
| 2026 | Leap month | 2nd Asadh: 15 July – 13 August |
| 2029 | Leap month | 2nd Asadh: 11 July – 9 August |
| 2030 | Leap day | Jesth has 30 days (15th waning day: 30 June) |
| 2031 | Leap month | 2nd Asadh: 20 July – 18 August |
| 2034 | Leap month | 2nd Asadh: 16 July – 14 August |
| 2035 | Leap day | Jesth has 30 days (15th waning day: 5 July) |
| 2037 | Leap month | 2nd Asadh: 13 July – 11 August |
| 2040 | Leap month | 2nd Asadh: 9 July – 7 August |
Calculated with the traditional Khmer calendar rules. In these years a leap day and a leap month never fall in the same year. Years not listed are normal 354-day years.
Is a year a Khmer leap year?
Enter a year from 1900 to 2059. The checker looks through that year with the Khmer calendar rules and shows whether it has an extra month, an extra day, or neither.
Frequently Asked Questions
What is Athikameas?
Athikameas is a Khmer leap-month year. The month of Asadh is repeated, as Pathamasadh (1st Asadh) and Tutiyasadh (2nd Asadh), so the year has 13 months and 384 days.
What is Chantreathimeas?
Chantreathimeas is a Khmer leap-day year: the month of Jesth has 30 days instead of 29, and the year has 355 days.
Is 2026 a leap year in the Khmer calendar?
Yes. 2026 has a leap month: the second Asadh ran from 15 July to 13 August 2026.
Is 2027 a Khmer leap year?
No. The calendar rules give 2027 as a normal year, with one Asadh from 4 July to 2 August. The next leap month comes in 2029.
Why was Pchum Ben so late in 2026?
Because of the second Asadh. Every month after it was pushed back by 30 days compared with a normal year, so Pchum Ben came on 11 October instead of in September.
Why is the extra month always Asadh?
That is the rule of the traditional Khmer calendar: in a leap-month year Asadh is the month that repeats, and the rains retreat, Chol Vassa, then begins after the second Asadh.
How do I find whether my birth year had a leap month?
Enter it in the checker above. The Khmer Calendar shows the months of any year, including 1st and 2nd Asadh.
Read next: how the Khmer lunar calendar counts days, Khmer animal year and Sak, or Cambodian public holidays 2026.
For cultural interest. Leap years are calculated with the traditional Khmer calendar rules; a national or pagoda calendar is the final word for ceremonies.
Sources
- All leap years, month ranges and festival dates: traditional Khmer calendar rules in the open-source momentkh library.
- Seven extra months in every 19 years in the Buddhist lunisolar calendars: Wikipedia, “Buddhist calendar”.
