Dictionary term
Intercalary Month
Direct answer
Intercalary Month: An Intercalary Month is an additional month inserted in some lunisolar calendars so lunar months remain near the same seasons.
An Intercalary Month is a leap month used to reconcile lunar months with the solar year.
An Intercalary Month is a leap month used to reconcile lunar months with the solar year.
A cycle or timeline schematic for comparing the named timekeeping concept.Quick reference
- Use when
- Use Intercalary Month when comparing Hebrew, Chinese, Babylonian, and other lunisolar calendar structures.
- Do not use it for
- Do not assume leap months share one name, position, or rule across lunisolar traditions.
- Reference category
- Calendars & Timekeeping
- Related terms
- Intercalary Day, Epact, Calendar, Julian Date
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The story behind Intercalary Month
Several ancient calendars moved from ad hoc observation to patterned leap-month cycles as astronomical prediction improved.
Intercalary Month in spiritual tradition
Spiritually, the leap month reflects patient reconciliation between two natural rhythms.
Intercalary Month: fact and faith, kept distinct
This is a factual calendar, astronomy, Earth-science, cultural-history, or observational reference. It can support wonder and practical planning without becoming a claim of fate, spiritual causation, or private revelation.
Intercalary Month in numerology
Intercalary Month is not a numerology claim. Any numbers attached to it should retain their ordinary scientific, calendrical, navigational, or historical meaning unless a separate symbolic interpretation is clearly labeled.
Why Intercalary Month matters
Twelve synodic months are about eleven days shorter than a seasonal year, so periodic leap months prevent long-term seasonal drift.
Intercalary Month at work: an example
A lunisolar calendar can place a thirteenth month in selected years of a nineteen-year cycle.
Where interpretation stops
Intercalary Month is presented as sourced astronomy, calendrical, Earth-science, cultural, or instrument-history reference. Definitions should distinguish measured phenomena from civil convention and historical interpretation, preserve location and time dependencies, and avoid turning factual sky data into a deterministic personal claim.
Sources and editorial method
Research references used for this entry include:
- U.S. Naval Observatory: Introduction to Calendars - Official overview of calendar systems, leap rules, eras, and historical calendar reform.
- U.S. Naval Observatory: Astronomical Almanac Glossary - Reference definitions for astronomical periods, coordinates, dates, and time scales.
- Source
- The Great Almanac Dictionary
- Category
- Calendars & Timekeeping
- Also appears in
- Calendars & Timekeeping
- Aliases
- None listed
- Last updated
- 2026-07-16
Trace the lunisolar leap cycle
Intercalary Month in a book is one thing; Intercalary Month in your own birth chart is your life. The Oracle casts your real chart and tells you what it means for your love, your work, and your year ahead, in conversation, free.
Speak with the OracleRelated terms
More in Calendars & Timekeeping
- Leap Year
- New Style Date
- Sidereal Month
- Tropical Year
- Apparent Solar Day
- Calendar Year
- Double Dating
- Era
Common questions
What is Intercalary Month?
An Intercalary Month is an additional month inserted in some lunisolar calendars so lunar months remain near the same seasons.
How is Intercalary Month used in an almanac?
Use Intercalary Month when comparing Hebrew, Chinese, Babylonian, and other lunisolar calendar structures.
What should I avoid when interpreting Intercalary Month?
Do not assume leap months share one name, position, or rule across lunisolar traditions.
