Thai astrological calendar (suriyayat)

A Thai astrological calendar in the suriyayat tradition: the days on which the sun moves into each sign, when the zodiac year changes, and how the waxing and waning days of the Thai lunar calendar are counted. It is background for casting a Thai chart, which uses sign-change days that differ from the everyday international calendar.

When the sun moves into each sign during the year

Sign-change dates follow the sidereal system commonly used in Thailand and may be a day off in some years. People born right on a sign-change day should check the astrological almanac for that year.

Days on which the sun changes sign in the Thai astrological calendar
Sign	Dates	Element
Aries	13 April – 13 May	Fire
Taurus	14 May – 13 June	Earth
Gemini	14 June – 14 July	Air
Cancer	15 July – 16 August	Water
Leo	17 August – 16 September	Fire
Virgo	17 September – 16 October	Earth
Libra	17 October – 15 November	Air
Scorpio	16 November – 15 December	Water
Sagittarius	16 December – 14 January	Fire
Capricorn	15 January – 12 February	Earth
Aquarius	13 February – 13 March	Air
Pisces	14 March – 12 April	Water

Zodiac years in the Thai calendar

2025 (BE 2568): Year of the Snake
2026 (BE 2569): Year of the Horse
2027 (BE 2570): Year of the Goat

The zodiac year changes at Songkran, around 13 April.

Check whether you clash with this year on the chong year page.

Thai month names and the international months

Thailand's international months carry names taken from the signs of the zodiac: names ending in -khom have 31 days, those ending in -yon have 30, and Kumphaphan has 28 or 29. The Thai lunar calendar is different again: its months are numbered from month 1 (duean ai) to month 12 and do not line up with the international months, because they follow the moon.

1. January: Mokarakhom (31 days)
2. February: Kumphaphan (28-29 days)
3. March: Minakhom (31 days)
4. April: Mesayon (30 days)
5. May: Phruetsaphakhom (31 days)
6. June: Mithunayon (30 days)
7. July: Karakadakhom (31 days)
8. August: Singhakhom (31 days)
9. September: Kanyayon (30 days)
10. October: Tulakhom (31 days)
11. November: Phruetsachikayon (30 days)
12. December: Thanwakhom (31 days)

How waxing and waning days are counted

One lunar cycle lasts about 29 and a half days, divided into a waxing half of 15 days and a waning half of 14 or 15 days. The 15th waxing day is the full moon and the 15th waning day is the dark moon. Thai Buddhist holy days fall on the 8th and 15th waxing days and the 8th and 15th (or 14th) waning days. The count is still used to set religious holidays and auspicious timings in Thai astrology.

Frequently asked questions

What is suriyayat?

It is the treatise Thai astrology uses to calculate the positions of the sun and planets, including the day on which the sun enters each sign. The astrological calendars Thai astrologers use are based on it, unlike the international calendar used in daily life.

Why do Thai sign-change dates differ from the Western ones?

Because Thailand uses the sidereal system, which follows the actual fixed stars in the sky, while the Western tropical system follows the spring equinox. The difference keeps growing and is now about 24 degrees, or roughly 24 days.

How are waxing and waning days counted?

The waxing half is when the moon grows brighter from the dark moon to the full moon, counted as the 1st to the 15th waxing day. The waning half is when the light decreases, counted as the 1st to the 14th or 15th waning day. A full cycle is about 29 and a half days.

On which day exactly does the Thai zodiac year change?

In royal tradition the zodiac year changes at Songkran, around 13 to 15 April, unlike the Chinese zodiac year, which changes at Lunar New Year between January and February.

More Calendars and references tools

All readings are personal belief based on astrological lore, presented for entertainment only. They are not medical, financial or legal advice and not gambling. Please use your own judgement.

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