Era-based year systems don’t always line up with the calendar on your phone. Japan, Taiwan, and Thailand often date documents and observances using Reiwa/Heisei-era years, Minguo (ROC) years, and the Buddhist Era—each with its own rules. This guide shows how to convert them to Gregorian dates quickly and correctly, with real-world examples and pitfalls to avoid.

What are era-based year systems?

Era-based systems count years from a specific starting point other than the traditional Anno Domini/Common Era (AD/CE). In Japan, years restart with each emperor’s era (Reiwa, Heisei, Showa). Taiwan counts from the founding of the Republic of China (Minguo, Year 1 = 1912). Thailand uses the Buddhist Era (BE), typically 543 years ahead of CE. Understanding these systems helps you match dates for “On This Day” posts, birthdays, and national observances with precision.

Why this matters for your calendar—and your content

• “On This Day” entries: A Japanese source might list an event as Heisei 31 (平成31年) in early 2019, while a Thai source shows BE 2562 for the same CE year.
• Birthdays and anniversaries: Official documents in Japan (戸籍, licenses), Taiwan (ID, household registration), and Thailand (government forms) often use era-based years.
• National observances: Holidays and commemorations are sometimes referenced in local year systems in press releases and media.

Quick conversion cheat sheet

Japan (Japanese era years, 和暦, wareki)

• Reiwa (令和): Started 2019-05-01. Formula: Gregorian year = Reiwa year + 2018. Example: Reiwa 7 (R7) → 2025.
• Heisei (平成): 1989-01-08 to 2019-04-30. Formula: Gregorian year = Heisei year + 1988. Example: Heisei 31 (H31) → 2019 (until 2019-04-30).
• Showa (昭和): 1926-12-25 to 1989-01-07. Formula: Gregorian year = Showa year + 1925. Example: Showa 64 (S64) → 1989 (only 1989-01-01 to 1989-01-07).
• Taisho (大正): 1912-07-30 to 1926-12-24. Formula: Gregorian year = Taisho year + 1911.
• Gannen (元年) note: Year “1” of an era may be written as 元年. Example: 令和元年 = Reiwa 1 (2019-05-01 to 2019-12-31).

Taiwan (Minguo, ROC calendar, 民國)

• Start: Minguo Year 1 = 1912.
• Formula: Gregorian year = Minguo year + 1911; Minguo year = Gregorian year − 1911.
• Example: 民國114年 (Minguo 114) → 2025; 109.02.28 → 2020-02-28.
• Format tips: You may see separators like 110/06/15 or 110.06.15; months/days are Gregorian.

Thailand (Buddhist Era, พ.ศ., BE)

• Modern rule (from 1941-01-01): BE = CE + 543; CE = BE − 543.
• Example: BE 2568 → 2025; 01/01/2568 → 2025-01-01.
• Older dates (1913–1940): New year was April 1. For BE dates in Jan–Mar, use CE = BE − 542; for Apr–Dec, CE = BE − 543.
• Thai numerals: ๐ ๑ ๒ ๓ ๔ ๕ ๖ ๗ ๘ ๙ correspond to 0–9. Example: ๒๕๖๘ = 2568.

Japan’s Reiwa and earlier eras: how to convert with confidence

Japan’s official documents often use era names (gengō). Each era begins on the day an emperor’s reign starts, and its Year 1 runs only from that start date to December 31. From January 1, the next ordinal year begins. That means 2019 spans two eras: Heisei 31 (until April 30) and Reiwa 1 (from May 1).

Key boundaries to remember

• Showa → Heisei: 1989-01-07 is Showa 64; 1989-01-08 becomes Heisei 1.
• Heisei → Reiwa: 2019-04-30 is Heisei 31; 2019-05-01 becomes Reiwa 1.

Practical examples

• R7/03/14 → Reiwa 7 → 2018 + 7 = 2025 → 2025-03-14.
• 平成31年4月12日 (Heisei 31/04/12) → 1988 + 31 = 2019 → 2019-04-12.
• 昭和64年1月5日 (Showa 64/01/05) → 1925 + 64 = 1989 → 1989-01-05 (only valid up to 1989-01-07).
• 令和元年6月3日 (Reiwa 1/06/03) → 2019-06-03 (元年 = Year 1).

Formatting and parsing tips

• Abbreviations: R (令和), H (平成), S (昭和), T (大正) often appear on forms: R07/05/01.
• Japanese numerals: Dates can appear in kanji: 令和七年五月一日 → R7/05/01.
• No year zero: Eras start at 1 (or 元); there is never a “Year 0.”
• Local time: Assign era by Japan Standard Time (JST). A birth late on April 30, 2019 JST is still Heisei 31.

Taiwan’s Minguo (ROC) years made simple

Taiwan counts years from 1912, the founding of the Republic of China. The months and days align with the Gregorian calendar, so you only need to convert the year.

One-line formula

• Minguo → Gregorian: add 1911. Example: 114 → 2025.
• Gregorian → Minguo: subtract 1911. Example: 2025 → 114.

Real-world examples

• 民國114年5月1日 → 114 + 1911 = 2025 → 2025-05-01.
• 110/06/15 → 110 + 1911 = 2021 → 2021-06-15.
• 109.02.29 → 109 + 1911 = 2020 → 2020-02-29 (leap day).

Parsing pitfalls

• Separators vary: 110/6/5, 110-06-05, and 110.06.05 are common. The order remains Y/M/D.
• Text markers: 中華民國 or 民國 may precede the year (民國114年). Sometimes just “年/月/日” characters wrap numerals.
• Historic nuance: Minguo Year 1 is 1912. For events pre-1912, do not apply Minguo conversion.

Thailand’s Buddhist Era (BE): the 543-year shift—and the exceptions

Modern Thai dates use the Buddhist Era, abbreviated พ.ศ. (Phuttha Sakarat). In contemporary practice, BE = CE + 543, with months and days aligned to the Gregorian calendar. For most modern uses—deadlines, licenses, press releases—subtract 543 to get the CE year.

Modern conversion

• BE → CE: CE = BE − 543. Example: 2568 → 2025; 10/12/2568 → 2025-12-10.
• CE → BE: BE = CE + 543. Example: 2025 → 2568.

Older dates (1913–1940): the April 1 new year

From 1913 until 1940, Thailand’s official new year was April 1. In that span:

• For BE dates in January–March: CE = BE − 542.
• For BE dates in April–December: CE = BE − 543.

On 1941-01-01, Thailand shifted the new year to January 1, and BE 2484 began on that day, making BE 2483 a short year (1940-04-01 to 1940-12-31).

Thai numerals and formatting

• ๐ ๑ ๒ ๓ ๔ ๕ ๖ ๗ ๘ ๙ = 0 1 2 3 4 5 6 7 8 9. Example: ๓๑/๑๒/๒๕๖๘ → 31/12/2568.
• Look for “พ.ศ.” before the year: พ.ศ. 2568 = BE 2568.

Applying conversions to real tasks

“On This Day” and editorial calendars

• Check boundaries: Events on 1989-01-07 (Showa 64) versus 1989-01-08 (Heisei 1) matter for Japanese sources.
• Use local time zones: Match the event to the local date (JST for Japan, CST for Taiwan, ICT for Thailand).
• Normalize in your CMS: Store ISO 8601 Gregorian dates, keep original era string as a note for display.

Birthdays and ID documents

• Japan: R07.03.14 on a form is 2025-03-14; H01 means 1989 from 1989-01-08 onward; S64 exists only through 1989-01-07.
• Taiwan: 095/12/30 is 2006-12-30. Leading zeros are common in ROC year formatting.
• Thailand: 14/02/2565 is 2022-02-14. Watch for Thai numerals on printed documents.

Common pitfalls to avoid

• Ignoring era start dates: Not every Gregorian year maps 1:1. 2019 includes H31 and R1.
• Assuming BE always = CE + 543 for all history: Pre-1941 dates may require the Jan–Mar adjustment (CE = BE − 542).
• Misreading Year 1 as 0: Japanese gannen (元年) is Year 1. There is no Year 0.
• Locale numerals: Thai digits and Japanese kanji numerals can break parsers; translate numerals first.
• Ambiguous slashes: In these systems, 110/06/05 (ROC) is Y/M/D, not U.S.-style M/D/Y.
• Leap days: Leap years follow the Gregorian rules. Example: ROC 109-02-29 = 2020-02-29; Japan’s wareki follows Gregorian month/day and leap rules.

Quick reference examples

• Reiwa 7 (R7) = 2025; R7/01/01 = 2025-01-01.
• Heisei 31 (H31) = 2019 (until 2019-04-30). H31/04/15 = 2019-04-15.
• Showa 64 (S64) = 1989 (only 1989-01-01 to 1989-01-07). S64/01/07 = 1989-01-07.
• Minguo 114 (ROC 114) = 2025; 114/05/20 = 2025-05-20.
• BE 2568 = 2025; 31/12/2568 = 2025-12-31.
• Historical BE example: 15/03/2482 (BE) → month is March (Jan–Mar rule) → CE = 2482 − 542 = 1940 → 1940-03-15.

Reliable mental math and a simple workflow

• Japan: Identify the era (R/H/S/T), convert with +2018/+1988/+1925/+1911, then verify the date falls within the era’s actual start/end.
• Taiwan: Add 1911 (or subtract to go the other way). The rest is standard Gregorian.
• Thailand: Subtract 543 (modern). If the BE year is 2483 or lower and the month is Jan–Mar, consider the CE = BE − 542 rule.
• Always store ISO 8601: Keep your canonical value as YYYY-MM-DD (Gregorian), with the original era-form date as metadata.

FAQ

How do I convert Reiwa 7 to a Gregorian year?

Reiwa year + 2018 → 7 + 2018 = 2025. So Reiwa 7 is 2025.

What is Minguo (ROC) year 114 in the Gregorian calendar?

Add 1911: 114 + 1911 = 2025. ROC 114 corresponds to 2025.

BE 2568 equals what year AD/CE?

Subtract 543: 2568 − 543 = 2025. Thai BE 2568 is AD 2025.

Does Japan always use era years? Can I see Western years too?

Both appear. Government forms often use era years, while media and international contexts frequently use Gregorian years. Always check the label (e.g., 令和, 平成) on official documents.

What about Showa 64 and Heisei 1—aren’t they both in 1989?

Yes. Showa 64 covers only 1989-01-01 to 1989-01-07; Heisei 1 begins 1989-01-08. Era changes split Gregorian years.

Why are older Thai BE dates tricky?

From 1913 to 1940, the Thai new year was April 1, not January 1. For BE dates in Jan–Mar of that period, use CE = BE − 542; otherwise CE = BE − 543. From 1941 onward, always subtract 543.

How do I parse ROC dates like 109.02.29 or 110/6/5?

Treat them as Y/M/D with Minguo years. 109.02.29 is 2020-02-29; 110/6/5 is 2021-06-05. If in doubt, look for markers like 民國 or 年/月/日.