# Date and time notation in Thailand

Thailand has adopted ISO 8601 under national standard: TIS 1111:2535 in 1992. However, Thai date and time notation reflects the country’s cultural development through the years used. The formal date format is D/M/YYYY format (1/6/2568), nowadays using the Buddhist Era (BE). The full date format is day-month-year format which is written in Thai (๑ มิถุนายน พ.ศ. ๒๕๖๘ or 1 มิถุนายน พ.ศ. 2568). While a 24-hour system is common for official use, colloquially, a 12-hour format with terms like "morning" (Thai: เช้า; RTGS: chao) and "night" (ค่ำ, kham), etc., or a modified six-hour format is used.

## Date

Thailand uses the Thai solar calendar as the official calendar, in which the calendar's epochal date (Year zero) was the year in which the Buddha attained parinibbāna. This places the current year at 543 years ahead of the Gregorian calendar. The year 2025 AD is indicated as 2568 BE in Thailand. Despite adopting ISO 8601, Thai official date is still written in D/M/YYYY formats, such as 30 January 2567 BE (2024 AD) or 30/1/2567. Anno Domini may be used in unofficial context, and is written in the same format (D/M/YYYY).
In full date format, the year is marked with "พ.ศ." (Buddhist Era) or "ค.ศ." (Anno Domini) to avoid confusion. As each calendar is 543 years apart, there is very little confusion in the contemporary context.

### Day in thai

Day in a week(Thai : สัปดาห์, pronounced [S̄ạpdāh̄̒]) according to the ISO 8601 international standard, Monday is designated as the first day of the week, while Sunday is considered as the last day. Meanwhile, in Thailand, Sunday was considered the start of the week, which ended on Saturday.
| English | Thai | RTGS | Abbr. |
| Sunday | วันอาทิตย์ | Wan Athit | อา. |
| Monday | วันจันทร์ | Wan Chan | จ. |
| Tuesday | วันอังคาร | Wan Angkhan | อ. |
| Wednesday | วันพุธ | Wan Phut | พ. |
| Thursday | วันพฤหัสบดี | Wan Phruehatsabodi or Pharuehatsabodi | พฤ. |
| Friday | วันศุกร์ | Wan Suk | ศ. |
| Saturday | วันเสาร์ | Wan Sao | ส. |

### Month in thai

In Thai, the names of months can be categorized based on the number of days they contain. Months with 30 days typically end with the suffix -yon (-ยน), while those with 31 days end with -khom (-คม). An exception is February, which is designated with the suffix -phan (-พันธ์) and has either 28 or 29 days depending on whether it is a leap year, as determined by the solar leap year system, referred to as pi athikasuratin (ปีอธิกสุรทิน).
| No. | English | Thai | RTGS | Abbr. |
| 1 | January | มกราคม | Makarakhom or Mokkarakhom | ม.ค. |
| 2 | February | กุมภาพันธ์ | Kumphaphan | ก.พ. |
| 3 | March | มีนาคม | Minakhom | มี.ค. |
| 4 | April | เมษายน | Mesayon | เม.ย. |
| 5 | May | พฤษภาคม | Pruetsaphakhom | พ.ค. |
| 6 | June | มิถุนายน | Mithunayon | มิ.ย. |
| 7 | July | กรกฎาคม | Karakadakhom or Karakkadakhom | ก.ค. |
| 8 | August | สิงหาคม | Singhakhom | ส.ค. |
| 9 | September | กันยายน | Kanyayon | ก.ย. |
| 10 | October | ตุลาคม | Tulakhom | ต.ค. |
| 11 | November | พฤศจิกายน | Phruetsachikayon | พ.ย. |
| 12 | December | ธันวาคม | Thanwakhom | ธ.ค. |

### Year in thai

The Thai calendar has evolved significantly throughout the nation's history, from their culture and tradition. Each era has been used to mark the passage of time, reflecting the historical and religious influences of the era.

#### Buddhist Era

The lunar calendar (Thai: ปฏิทินจันทรคติ; RTGS: patithin chantharakhati) system is based on the cycles of the moon. A lunar month lasts about 291/2 days, and the year consists of 12 months with the occasional insertion of an extra month (13th month) to keep the lunar and solar years aligned. Each month is divided into two phases the waxing moon (ข้างขึ้น; khang khuen) and the waning moon (ข้างแรม; khang raem).
The traditional Thai lunar calendar follows the Buddhist Era (พุทธศักราช; phutthasakkarat), which is 543 years ahead of the Gregorian calendar.
Important dates on the Thai calendar were often connected to Buddhism, such as Vesakha Puja (วันวิสาขบูชา; wan wisakhabucha), which commemorates the birth, enlightenment, and passing of the Buddha. These holidays are determined by the lunar calendar.

#### Shaka era

Shaka era (Thai: มหาศักราช; RTGS: Mahasakkarat) is widely used in historical evidence such as stone inscriptions and chronicles from both the Sukhothai and early Ayutthaya periods. Shaka era was established by King Kanishka of the Kushan dynasty, beginning after the Buddhist Era 622 (Shaka era corresponds to 622 CE).

#### Chula Sakarat

Chula Sakarat (Thai: จุลศักราช; RTGS: Chulasakkarat) is an era influenced by Burma. The king of Pagan first started using it in Burma in 1182 CE and it spread to the Lan Na Kingdom starting after 1181 CE. Thais like to use Chula Sakarat in astrological calculations and to indicate the year in inscriptions, legends, records, and chronicles until the time of King Chulalongkorn when he announced its abolition and used Rattanakosin Era instead.

#### Rattanakosin Era

The Ratanakosin Era (RS, Thai: รัตนโกสินทร์ศก, RTGS: Rattanakosinsok) was established on 1 April 1889 by Chulalongkorn, starting with the year Bangkok was declared as the capital as 1 RS. Thailand continued the Rattanakosin Era until 131 RS. It was announced to be canceled during the early reign of King Vajiravudh, eventually being turned into the Buddhist Era instead.

#### Gregorian year

The Buddhist calendar is widely used in Southeast Asian countries that follow the Theravada school of Buddhism, particularly in Thailand, Cambodia, Laos, Myanmar, and Sri Lanka. In Thailand, it was formally adopted in 2455 BE (1912 AD), during the reign of Vajiravudh, replacing the Rattanakosin Era. Although it has been in use since the Ayutthaya period, it continues to be used today. The Buddhist Era (BE) starts one year after the Buddha's parinirvana, making the Buddhist calendar 543 years ahead of the Gregorian calendar.

#### Year calculation

* Buddhist Era = Anno Domini + 543
* Buddhist Era = Maha Sakarat + 621
* Buddhist Era = Chula Sakarat + 1181
* Buddhist Era = Rattanakosin Era + 2324

### Thai numerals in Thai official document

Thai numerals are commonly used in official government documents in Thailand for conserving Thai cultures and it is in a day month year format by day and year are written in Thai numerals and month is written in Thai. Additionally, in the official documents, year is written in the Buddhist era. For example, to write a full date format, 1 June 2013, in Thai government documents, ๑ มิถุนายน พ.ศ. ๒๕๕๖.
| Arabic | Thai numerals | RTGS | Thai |
| 0 | ๐ | sun | ศูนย์ |
| 1 | ๑ | nueng | หนึ่ง |
| 2 | ๒ | song | สอง |
| 3 | ๓ | sam | สาม |
| 4 | ๔ | si | สี่ |
| 5 | ๕ | ha | ห้า |
| 6 | ๖ | hok | หก |
| 7 | ๗ | chet | เจ็ด |
| 8 | ๘ | paet | แปด |
| 9 | ๙ | kao | เก้า |
| 10 | ๑๐ | sip | สิบ |

### Colloquialism in Thailand
#### Date colloquialism in Thailand

The time points of days in the past, present, and future, which are found in the Thai language, are expressed using various words, including:
* Past:
** "เมื่อวาน" (RTGS: muea wan) refers to yesterday or one day before today.
** "เมื่อวานซืน" (RTGS: muea wan suen) refers to the day before yesterday or two days before today.
* Present:
** "วันนี้" (RTGS: wan ni) refers to today.
* Future:
** "พรุ่งนี้" (RTGS: phrung ni) refers to tomorrow or one day after today.
** "มะรืนนี้" (RTGS: maruen ni) refers to the day after tomorrow or two days after today.
** "มะเรื่อง" (RTGS: marueang) refers to three days after today.

#### Month colloquialism

The time points of months in the past, present and future, which are found in Thai language, are expressed using many words, including:
* Past:
** "เดือนที่ผ่านมา" (RTGS: duean thi phan ma) refers to previous month or last month.
** "เดือนที่แล้ว" (RTGS: duean thi laeo) refers to previous month or last month.
** "เดือนก่อน" (RTGS: duean kon) refers to previous month or last month.
** "เดือนที่แล้วมา" (RTGS: duean kon) refers to a month that came before the last month but does not specify an exact time frame.
* Present:
** "เดือนนี้" (RTGS: duean ni) refers to this month.
* Future:
** "เดือนหน้า" (RTGS: duean na) refers to next month or one month after the current month.
** "เดือนถัดไป" (RTGS: duean that pai) refers to next month or one month after the current month.
** "เดือนหน้านู้น" (RTGS: duean na nun) refers to the month two months from now, two months after the current month or more.

#### Year colloquialism

The time points of years in the past, present and future, which are found in Thai language, are expressed using many words, including:
* Past:
** "ปีก่อน" (RTGS: pi kon) refers to the year before last or one year before the current year.
** "ปีที่แล้ว" (RTGS: pi thi laeo) refers to the year before last or one year before the current year.
** "ปีกลาย" (RTGS: pi klai) refers to more than one year before the current year, but it does not specify exactly how many years ago.
* Present:
** "ปีนี้" (RTGS: pi ni) refers to this year.
* Future:
** "ปีหน้า" (RTGS: pi na) refers to next year or one year after the current year.
** "ปีถัดไป" (RTGS: pi that pai) refers to next year or one year after the current year.

## Time

There are two systems of telling time in Thailand. Official time follows a 24-hour clock. The 24-hour clock is commonly used in military, aviation, navigation, meteorology, astronomy, computing, logistical, emergency services, and hospital settings, where the ambiguities of the 12-hour clock cannot be tolerated.
In the second, everyday usage, the day is divided into four six-hour periods.$^{:101}$ Additional words are used to identify the period specified (similar to a.m. or p.m. for a 12-hour system).
The distinguishing words are:
* 00:00-00:59 = เที่ยงคืน (RTGS: thiang khuen)
* 01:00-05:59 = ตี (RTGS: ti)
* 06:00-11:59 = โมงเช้า (RTGS: mong chao)
* 12:00-12:59 = เที่ยง (RTGS: thiang)
* 13:00-15:59 = บ่ายโมง (RTGS: bai mong)
* 16:00-18:59 = โมงเย็น (RTGS: mong yen)
* 19:00-23:59 = ทุ่ม (RTGS: thum)
Thailand is in the UTC+07:00 time zone, which is also known as Indochina Time (ICT) and military time zone Golf.

### Thai six-hour clock

The Thai six-hour clock divides the day into four distinct 6-hour periods and reflects traditional Thai customs. While modern Thailand primarily uses the 24-hour clock for official purposes, this system remains a cultural heritage from earlier Thai norms. It is still occasionally used in informal settings, especially in rural areas and casual conversation.
Notation of the Thai time system:
* The first six-hour period (01:00–06:00) is expressed using the numbers 1 through 6, followed by the phrase "ตี" (ti).
* The second six-hour period (07:00–12:59) is expressed using the numbers 1 through 6, followed by the phrase "โมงเช้า" (mong chao).
* The third six-hour period (13:00–18:59) is expressed using the numbers 1 through 6, followed by the phrase "บ่าย" (bai) or "โมงเย็น" (mong yen).
* The fourth six-hour period (19:00–00:59) is expressed using the numbers 1 through 6, followed by the phrase "ทุ่ม" (thum).
The terms mong and thum originate from the sounds produced by traditional Thai instruments: the gong and the drum, respectively. These sounds were historically used as signals to mark the passage of time. mong represents the sound of the gong, associated with signaling the day, while thum represents the sound of the drum, used to signify the night. This system of timekeeping was formalized during the reign of King Mongkut.

### Thai 24-hour clock

The 24-hour clock in Thai is used similarly to the international system, especially in formal contexts like transportation, news, military, and government. By expressing 00:00-23:59, followed by the phase "นาฬิกา" (RTGS: nalika)
| 24-hour numerical notation | Time | Modified 6-hour | Modified 6-hour | 24-hour | 24-hour |
| 24-hour numerical notation | Time | Thai | RTGS | Thai | RTGS |
| 24:00 or 00:00 | Midnight | เที่ยงคืน | thiang khuen | ยี่สิบสี่นาฬิกา or ศูนย์นาฬิกา | yi-sip-si nalika or sun nalika |
| 01:00 | 1 early morning | ตีหนึ่ง | ti nueng | หนึ่งนาฬิกา | nueng nalika |
| 02:00 | 2 early morning | ตีสอง | ti song | สองนาฬิกา | song nalika |
| 03:00 | 3 early morning | ตีสาม | ti sam | สามนาฬิกา | sam nalika |
| 04:00 | 4 early morning | ตีสี่ | ti si | สี่นาฬิกา | si nalika |
| 05:00 | 5 early morning | ตีห้า | ti ha | ห้านาฬิกา | ha nalika |
| 06:00 | 6 in the morning | หกโมงเช้า | hok mong chao | หกนาฬิกา | hok nalika |
| 07:00 | 7 in the morning | เจ็ดโมงเช้า | chet mong chao | เจ็ดนาฬิกา | chet nalika |
| 08:00 | 8 in the morning | แปดโมงเช้า | paet mong chao | แปด นาฬิกา | paet nalika |
| 09:00 | 9 in the morning | เก้าโมงเช้า | kao mong chao | เก้านาฬิกา | kao nalika |
| 10.00 | 10 in the morning | สิบโมงเช้า | sip mong chao | สิบ นาฬิกา | sip nalika |
| 11.00 | 11 in the morning | สิบเอ็ดโมงเช้า | sip-et mong chao | สิบเอ็ด นาฬิกา | sip-et nalika |
| 12:00 | Midday | เที่ยงวัน | thiang wan | สิบสองนาฬิกา | sip-song nalika |
| 13:00 | 1 in the afternoon | บ่ายโมง | bai mong | สิบสามนาฬิกา | sip-sam nalika |
| 14:00 | 2 in the afternoon | บ่ายสองโมง | bai song mong | สิบสี่นาฬิกา | sip-si nalika |
| 15:00 | 3 in the afternoon | บ่ายสามโมง | bai sam mong | สิบห้านาฬิกา | sip-ha nalika |
| 16:00 | 4 in the afternoon | บ่ายสี่โมง | bai si mong | สิบหกนาฬิกา | sip-hok nalika |
| 17:00 | 5 in the afternoon | ห้าโมงเย็น | ha mong yen | สิบเจ็ดนาฬิกา | sip-chet nalika |
| 18:00 | 6 in the evening | หกโมงเย็น | hok mong yen | สิบแปดนาฬิกา | sip-paet nalika |
| 19:00 | 1 at night | หนึ่งทุ่ม | nueng thum | สิบเก้านาฬิกา | sip-kao nalika |
| 20:00 | 2 at night | สองทุ่ม | song thum | ยี่สิบนาฬิกา | yi-sip nalika |
| 21:00 | 3 at night | สามทุ่ม | sam thum | ยี่สิบเอ็ดนาฬิกา | yi-sip-et nalika |
| 22:00 | 4 at night | สี่ทุ่ม | si thum | ยี่สิบสองนาฬิกา | yi-sip-song nalika |
| 23:00 | 5 at night | ห้าทุ่ม | ha thum | ยี่สิบสามนาฬิกา | yi-sip-sam nalika |