Baby Milestone Date Calculator
From a birthday, list oshichiya, miyamairi, okuizome, the first sekku and the half-birthday, each with its weekday. Dates are common rules of thumb; shrines and families vary.
Examples (click to try)
Pick a birthday to see the milestone dates
How to use
Pick a birthday and sex. The tool lists oshichiya, miyamairi, okuizome, the first sekku and the half-birthday with weekdays — a draft for photos and meals, not a confirmed date.
Counting (birthday = day 1)
- Oshichiya — +6 days (7th day); naming
- Miyamairi — shown as boy +30 (day 31), girl +31 (day 32); some shrines use 32/33
- Okuizome — shown as +99 days (day 100); some families use day 110 or 120
- First sekku — first 3 March (girl) or 5 May (boy) on or after birth; often the next year if very young
- Half-birthday — same day six months later (or month-end)
Example (born 15 Jan 2026)
- Oshichiya → 21 Jan 2026 (Wed)
- Miyamairi → boy 14 Feb (Sat), girl 15 Feb (Sun)
- Okuizome → 24 Apr (Fri)
- First sekku → boy 5 May, girl 3 March
- Half-birthday → 15 Jul (Wed)
Related tools
Due date: pregnancy due date. Counted-age rites: kazoedoshi. Ages 3–7: Shichi-Go-San.
FAQ
Is the birthday sent to a server?
No. Everything runs in your browser; nothing is transmitted or stored externally.
How many days after birth are oshichiya and okuizome?
The birthday is day 1. Oshichiya is 6 days later (the 7th day). Okuizome is shown as 99 days later (the 100th day); some families use day 110 for girls or day 120 in Kansai.
Does miyamairi differ for boys and girls?
The table uses one common count: day 31 for boys (birthday + 30) and day 32 for girls (birthday + 31). The Tokyo Jinjachō guide lists day 32 (or 31) for boys and day 33 for girls, so this is not the only nationwide custom. Confirm with the shrine.
When is the first sekku?
The table shows the first Girls’ Festival (3 March) or Boys’ Festival (5 May) on or after the birthday. Families often wait until the following year if the child is very young, even when born on that date.
How is the half-birthday calculated?
The same day of the month, six months later. If that day does not exist (for example 31 August), it snaps to the last day of the month.