The Thai solar calendar, Suriyakati (Thai: สุริยคติ), has been the official and prevalent calendar in Thailand since it was adopted by King Chulalongkorn in 1888, although the Western calendar year is sometimes used in business, and quite often in banking.
Thai calendars show both the Buddhist Era (BE, Thai: พุทธศักราช Phutthasakkarat), abbreviated Pho So (Thai: พ.ศ.); and the Christian Era (Thai: คริสต์ศักราช, Khritsakkarat) , abbreviated Kho So (Thai: ค.ศ.). They also show Chinese numerals for the Common Era and Chinese Lunar dates. As lunar dates determine Buddhist Sabbaths (Thai: วันพระ Wan Phra), as well as many Chinese traditional festivals, both lunar calendar and Chinese lunar dates are shown.
- A Buddha image marks Thai Sabbaths, Wan Phra; a red tablet bearing white Chinese characters marks New and Full Moons as calculated in China.
- Scrawled blue figures (in this example 078 on the 15th and, above left, 538 on the 19th and 2576 on the 31st) mark dates national lottery numbers were drawn.
- Lunar dates and the year's Animal are recorded on Thai birth certificates after the official date. The Thai reckon their ages by the Twelve-Animal sequence, though the official calendar determines age at law; as, for instance, the Queen's Birthday, August 12, a public holiday also celebrated as Thai Mothers' Day.
The months and days of the week are the same as those used in the western Gregorian calendar. Names of the months derive from Hindu names of the signs of the zodiac. Days of the week are named after the Sun and Moon, and translations of the names of the five classical planets. The year is counted from the Buddhist Era (B.E.), which is 543 years earlier than the Christian Era (A.D.). For example, A.D. 2007 is equivalent to 2550 B.E. The era is based on the passing away (Parinibbana) of Gautama Buddha, which is dated to 543 BC by the Thai (although some sources state that Buddha died in 483 BC). It is important to remember that only from January 1, 1941 onwards does this 543 addition/subtraction rule work perfectly
The calendar, decreed by King Chulalongkorn (Rama V), was called Rattanakosin Era (Thai: รัตนโกสินทรศก, Rattanakosin Sok), abbr. (Thai: ร.ศ.) Ro So), and was nearly identical with the western Gregorian calendar. Year counting, however, was in reference of the date of the founding of Bangkok (Rattanakosin), April 6, 1782 (the first day of Year 1 Rattanakosin Era). King Vajiravudh (Rama VI) changed the year counting to Buddhist Era in 1912 and fixed the start of a year to April 1.
In 1941 (2484 B.E.) Prime Minister Plaek Phibunsongkhram per decree made January 1 the official start of a new year (so year 2483 B.E. had only nine months). When converting a date prior to that year, check whether it falls between January 1 and March 31: if so the number to add or subtract is 542, not 543.
Today, both the Common Era New Year's Day (January 1) and the traditional Songkran (Thai: สงกรานต์) celebrations (April 13-15) are public holidays on the official calendar. Public holidays on the official calendar for Buddhist and Chinese feasts, including Chinese New Year, are still calculated according to the lunar calendar, so their dates change with respect to the solar calendar every year.
Months
Thirty-day-month names end with Thai: -อายน -ayon, which is from the Sanskrit root -āyana, meaning the arrival of; 31-day-month names with Thai: -อาคม -akhom, which is from Sanskrit -āgama which also means the arrival of. February's name ends with Thai: -พันธ์ -phan, from Sanskrit bandha fettered or bound. The day added to February in a solar leap year is called Athikasuratin Thai: อธิกสุรทิน; respelled to aid pronunciation Thai: อะทิกะสุระทิน.
| English | Thai | Abbr. | Transcription | Sanskrit | Zodiac Sign |
|---|---|---|---|---|---|
| January | มกราคม | ม.ค. | makarakhom | makara "sea-monster" | Capricorn |
| February | กุมภาพันธ์ | ก.พ. | kumphaphan | kumbha "pitcher, water-pot" | Aquarius |
| March | มีนาคม | มี.ค. | minakhom | mīna "(a specific kind of) fish" | Pisces |
| April | เมษายน | เม.ย. | mesayon | meṣa "ram" | Aries |
| May | พฤษภาคม | พ.ค. | phruetsaphakhom | vṛṣabha "bull" | Taurus |
| June | มิถุนายน | มิ.ย. | mithunayon | mithuna "a pair" | Gemini |
| July | กรกฎาคม | ก.ค. | karakadakhom | karkaṭa "crab" | Cancer |
| August | สิงหาคม | ส.ค. | singhakhom | siṃha "lion" | Leo |
| September | กันยายน | ก.ย. | kanyayon | kanyā "girl" | Virgo |
| October | ตุลาคม | ต.ค. | tulakhom | tulā "balance" | Libra |
| November | พฤศจิกายน | พ.ย. | phruetsachikayon | vṛścika "scorpion" | Scorpio |
| December | ธันวาคม | ธ.ค. | thanwakhom | dhanu "bow, arc" | Sagittarius |
Weeks
A week is Thai: สัปดาห์ or สัปดาหะ, pronounced สับ-ดา sàb-da or สับ-ดา-หะ sàb-da-hà. From a Sanskrit word for "seven", it is now defined by the On-line Royal Institute Dictionary (ORID) as a 7 day period beginning on Sunday and ending Saturday. When referring to Thai lunar calendar lunations, however, it is the 7-, 8- or (rarely) 9-day interval between quartile lunar phases; that is, from one วันพระ wan phrà to the next.
Weekdays
| Thai name | Transcription | Colour | Sanskrit | Planet | |
|---|---|---|---|---|---|
| Sunday | วันอาทิตย์ | wan athit | red | Aditya | Sun |
| Monday | วันจันทร์ | wan chan | yellow | Chandra | Moon |
| Tuesday | วันอังคาร | wan angkhan | pink | Angaraka | Mars |
| Wednesday | วันพุธ | wan phut | green | Budha | Mercury |
| Thursday | วันพฤหัสบดี | wan pharuehat (sabodi) | orange | Brihaspati | Jupiter |
| Friday | วันศุกร์ | wan suk | blue | Shukra | Venus |
| Saturday | วันเสาร์ | wan sao | purple | Shani | Saturn |
