Tenpō calendar

Today (at UTC+00)
Thursday, 27 August 2026
Japanese	15 Fumizuki, Reiwa 8 (Shosho, 11 days until Hakuro)
Other calendars Akan Foyaw Armenian 8 Hoṙi 1476 Aztec Atemoztli 9, 9 Ōlīn Babylonian 13 Abu, 2337 SE Balinese pawukon Luang, Pepet, Pasah, Jaya, Umanis, Tungleh, Wraspati of Matal, Kala, Urungan, Duka Bengali 12 Bhadro, BS 1433 Chinese Yin Water Rooster・Dipper Mansion 15 Qīyuè, Bǐngwǔnián (Chushu, 11 days until Bailu) Common Era 27 August 2026 CE Coptic 21 Mesori, AM 1742 Egyptian 13 Tybi, 2775 NE Ethiopian 21 Naḥasē, 2018 Amätä Məhrät French Republican Décade I, Décadi de Fructidor de l'Année 234 de la République Gregorian 27 August, AD 2026 Hebrew 14 Elul, AM 5786 Hindu Dhaniṣṭhā・Śobhana Solar: 11 Bhādrapada, 1948 SE Lunisolar: Caturdaśī, Śukla pakṣa of Śrāvaṇa, 2083 VE Rāudra・5127 KY・1,872,814 Icelandic Fimmtudagur, 3 Tvímánuður 2026 Islamic 13 Rabi' al-awwal, AH 1448 (using tabular method) ISO week date 2026-W35-4 Japanese 15 Fumizuki, Reiwa 8 (Shosho, 11 days until Hakuro) Julian 14 August, AD 2026 (AM 7534) Julian day 2461280 Maya 13.0.13.15.17 10 Mol, 9 Caban Roman ante diem XIX Kalendas Septembres, MMDCCLXXIX AUC Solar Hijri 5 Shahrivar, SH 1405 Tibetan 14 lhag gro bzhin, me pho rta 2153 or 1772 or 1000
[]

The Tenpō calendar (天保暦, Tenpō-reki), officially known as the Tenpō sexagenary unitary calendar (天保壬寅元暦 Tenpō jin'in genreki), was a Japanese lunisolar calendar. It was published in the Tenpō era (1830–1844). It remained in use throughout the late Edo period, from 1844 to 1872.

History

The Tenpō-reki system was developed by Shibukawa Kagesuke. It was the last calendar system devised by Japanese astronomers and mathematicians.

Overview

The Tenpō calendar is a lunisolar system which adopted the Teiki-hō method, dividing solar terms by solar longitude instead of time, unlike the previous Heiki-hō method. It begins each lunar month on the day of the new moon and adds a leap month when necessary, specifically when three lunar months occur between a solstice and equinox. Out of those three months, the one without a chūki 中気 is designated the leap month. Solstice and equinox consistently fall within the second, fifth, eighth and eleventh months. Observations from Kyoto dictates the time used for determining solar terms and lunar phases.

Unlike previous calendars with uniform hours lengths, the Tenpō calendars hour vary seasonally, posing the length of hours changed depending on the time of year. This made it extremely challenging to make Japanese mechanical clocks.

The Tenpō calendar is no longer officially maintained.

See also

• Japanese calendar
• Sexagenary cycle
• Tenpō

External links

• National Diet Library, "The Japanese Calendar"