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Tibetan · Wiki 36

Phugpa / Tsurphu / Kālacakra

Phugpa calendar tool

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How to use Phugpa Tibetan calendar

Convert between a Gregorian civil date and a date in the declared Phugpa calculation convention. The result keeps Tibetan year, month, lunar day, leap-month status and repeated-day occurrence together, so a calendar record can be compared without silently changing its convention.

Inputs: Choose one direction: a Gregorian civil date from 1900-01-01 through 2100-12-31, or a Western-numbered Tibetan year, month, lunar day and an explicit regular/leap month choice. A Tibetan year here is the Western-numbered year containing that year's Losar; it is not a Tibetan-era year. The date-only conversion has no time-zone or location selector.

  1. Choose Gregorian → Phugpa or Phugpa → Gregorian, then enter the date fields for that direction.
  2. For a Tibetan date, choose regular or leap month explicitly. A leap month is the first occurrence of two identically numbered months in this convention.
  3. Read the full returned label: year, month, lunar day, leap-month marker and any first/second occurrence marker.
  4. If a reverse lookup returns two dates for a repeated lunar day, choose the occurrence intended by the record; neither date is preselected.
  5. If a lunar-day label is omitted, keep the omission as the result. Do not move it to a nearby civil date.
  6. Download or copy the result with its named Phugpa convention and source version when comparing another calendar or record.
Calculated example · 2012 month 1

Calculated teaching example: in the published 2012 month-1 label pattern, day 5 is repeated and day 19 is omitted. Under this declared calculation, the two day-5 occurrences are 2012-02-26 and 2012-02-27. A reverse lookup therefore presents both dates for selection, while a lookup for month 1, day 19 reports no civil-date occurrence. These dates illustrate this declared calculation version; they are not an independently verified contemporary almanac claim.

This guide describes one Phugpa version: E1987 with Janson's a₂ = 1/28 coefficient. It does not establish parity with Tsurphu, Bhutanese, Mongolian or every contemporary Tibetan almanac, and it does not substitute modern observed lunar phases for the lineage calculation. A calculated calendar label is not a horoscope, personality reading, auspicious-day judgement or ritual adjustment. Published-reference fixtures check fidelity to Janson's equations and tables, not independent confirmation of every result.

Open Phugpa Tibetan calendar →All glossary terms →
Sources and conventions

History & development

Tibetan calendar calculation is associated with Kālacakra literature and later lineages. Janson's mathematical account distinguishes Phugpa from Tsurphu; they should be named separately rather than treated as a single interchangeable Tibetan calendar. Losar is also observed through varied Himalayan customs, so a calculated Phugpa year boundary does not determine every community's festival practice.

Mythology & symbolic world

Kālacakra, Wheel of Time, belongs to a Buddhist religious framework that connects temporal cycles and practice. Phugpa calendar arithmetic and community observances have related histories, but a computed civil date does not establish ritual authority. Losar customs vary across Himalayan communities; the calculator does not select a universal festival practice.

Provenance: where the rules come from

The Phugpa date workspace implements the E1987 epoch and a₂=1/28 coefficient in Svante Janson’s mathematical account. Its mean motions and corrections are calculated as exact rational quantities. The 425 published-reference checks establish fidelity to that account’s tables and examples; they do not certify every contemporary almanac or another Tibetan lineage.

How it is calculated

Named Phugpa E1987 construction: rational mean motions, corrections, lunar-day endings and Gregorian civil-date assignment.

Choices that change the result: Phugpa E1987, Janson a₂=1/28. Keep regular/leap month and repeated-day occurrence explicit. Tsurphu and other lineages remain separate.

Inspect your calendar date →

Uses & use cases

  • Convert a civil date into a complete Phugpa date label under the declared convention.
  • Identify both civil occurrences of a repeated lunar-day label, or preserve an omitted label.
  • Compare the month pattern and stated assumptions with a dated document or almanac.
  • Keep the exact calendar request, meanings, glossary and sources in a downloadable report.

Interpretation methods

Method 1

Read the complete calendar label

Open Phugpa date workspace, choose either conversion direction, and calculate. Read the Western-numbered Tibetan year, month, lunar day, leap-month marker and occurrence together. Your selected calendar request carries into this wiki; it is independent of your saved birth profile and zodiac settings.

Study example

Calculated teaching example: in the published 2012 month-1 label pattern, day 5 is repeated and day 19 is omitted. Under this declared calculation, the two day-5 occurrences are 2012-02-26 and 2012-02-27. A reverse lookup therefore presents both dates for selection, while a lookup for month 1, day 19 reports no civil-date occurrence. These dates illustrate this declared calculation version; they are not an independently verified contemporary almanac claim.

Method 2

Distinguish an omission from missing information

A date label with zero civil occurrences is an explicit calendar result. Leave it omitted instead of shifting it to the nearest date. A repeated label has two distinct civil occurrences; select one only if the source identifies it.

Study example

In the declared 2012 month-1 pattern, day 19 has no civil occurrence. Day 5 has two: 26 and 27 February. The month grid displays these outcomes separately.

Method 3

Compare sources without changing the lineage

Keep the named Phugpa version and epoch attached to every comparison. A difference from Tsurphu or a local almanac is a reason to inspect conventions; it is not permission to substitute Chinese lunar dates or modern observed Moon phases.

Study example

A Gregorian date can fall before Losar while belonging to the preceding Western-numbered Tibetan year. Retain both year labels in the record.

Explore these reading approaches

Historical and textual reconstruction ↗

Concepts in this tradition

Follow a term for its definition, word origin, evidence and connected ideas.

Phugpa / Tsurphu / Kālacakra →

Disagreements & limits

  • This guide describes one Phugpa version: E1987 with Janson's a₂ = 1/28 coefficient. It does not establish parity with Tsurphu, Bhutanese, Mongolian or every contemporary Tibetan almanac, and it does not substitute modern observed lunar phases for the lineage calculation. A calculated calendar label is not a horoscope, personality reading, auspicious-day judgement or ritual adjustment. Published-reference fixtures check fidelity to Janson's equations and tables, not independent confirmation of every result.
  • Gregorian input range: 1900–2100. Reverse lookup uses Western-numbered Tibetan years 1899–2100 and can be clipped at the supported civil-date boundaries.
  • Tsurphu, Bhutanese and Mongolian versions, full natal interpretation, auspicious-date rules and ritual adjustments are not supplied by this tool.

Sources & evidence

Practitioner sources describe their own systems. Historical and astronomical sources support different kinds of claims. Reading exercises are editorial teaching examples.

  1. Svante Janson · Tibetan calendar mathematics, §§3, 5–8 and Appendix A.1 ↗mathematical or cultural source; see individual scope
  2. Alexander Berzin · Tibetan Astro Sciences ↗mathematical or cultural source; see individual scope
  3. Westin Harris · Losar Celebrations Across Himalayan Cultures, Rubin Museum ↗mathematical or cultural source; see individual scope
  4. Men-Tsee-Khang · Tibetan calendar ↗mathematical or cultural source; see individual scope

Connected entries

Panchanga / drik calculation →Bhutanese / Mongolian / regional Tibetan calendars →Element / animal / mewa / parkha overlays →