Half-Birthday Calculator
Enter your baby's birth date to see all the little milestones worth celebrating — the half-birthday, the 100-day mark, the first birthday, and each monthly anniversary, with the day of the week for every one.
Pick a birth date to see the milestone dates.
Just for fun and planning. Dates are calculated from the birth date you enter.
How it works
Type in your baby's date of birth. Everything is worked out from that single date — nothing is read from today's clock, so you can plan ahead or look back freely.
The half-birthday is exactly six calendar months after the birth date, and the first birthday is twelve months after. The 100-day mark counts the birth day as day one (a tradition in many cultures), so it lands 99 days later.
We also list each monthly anniversary, from one month up to a full year, and show the weekday for every date so you can pick a good day to celebrate.
Frequently asked questions
When is my baby's half-birthday? +
It's the date exactly six months after the day your baby was born. For example, a baby born on March 10 has a half-birthday on September 10.
Why is the 100-day date 99 days after birth? +
In the 100-day tradition the birth day itself counts as day one, so day 100 falls 99 days later. Many families mark it as a happy milestone.
What is a month-iversary? +
It's a playful name for each monthly anniversary of the birth — one month old, two months old, and so on. Lots of parents snap a photo on each one during the first year.
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