Born in a Leap Month? Here's How to Cast Your Chart
People born in a lunar leap month hit a real question when casting:
does the leap month count as this month or the next? It's not
pedantry — BaZi and Zi Wei answer differently, and mixing them up
misdraws the chart.
Two systems, two rules
BaZi follows solar terms, not lunar months.
The BaZi month pillar is bounded by solar terms: Lichun-to-Jingzhe is
Yin month, Jingzhe-to-Qingming is Mao month, and so on. A leap month is
just the lunar calendar's correction for the tropical year — solar
terms don't leap. So BaZi casting for leap-month births is simple:
look at the solar term in effect on your birthday. No debate.
Zi Wei follows the lunar month, and schools disagree.
Zi Wei Dou Shu sets palaces by lunar month, so the leap-month question
is real and schools split into two conventions:
- Leap counts as the same month: leap-fifth-month reads as month 5.
The leap is "extra" and follows the month it duplicates
- Leap counts as the next month: leap-fifth reads as month 6.
The reasoning: the mid-qi has already passed, so the month-qi has moved
The two conventions put the Life palace in different places — it's a
schools' agreement, not a right/wrong question. Traditional San He
schools mostly use "same month"; our engine defaults to it.
Practical advice for leap-month births
- Cast first with the default (same-month) convention and check whether
the Life-palace description sounds like you
- If it feels off, re-cast manually shifting the birth month forward
and compare — the chart that matches your known temperament wins
(same cross-check method as for uncertain birth hours)
- BaZi needs no workaround — solar terms handle it automatically
Do you even have a leap-month birthday?
Check the lunar year: 2025 had a leap sixth month, 2023 a leap second,
2017 a leap sixth. If family records say "lunar month X" and that year
had a leap X, confirm whether it was the regular or the leap one —
one word changes the whole chart.
Our forms take a Gregorian date and convert internally (leap months
included) — you only need the birthday itself to be right.