Counts the days since a birth date and gives the dates of the 100th and 1000th day. The day of birth counts as day one, so the 100th day falls 99 days after it.
This tool counts the days since a birth and gives the dates of the 100th and the 1000th day. In Japan the hundredth day carries a meal ceremony called okuizome, and elsewhere the same counting turns up wherever an age in days is wanted.
Here is the day number of the birth, that of the reference date and the days since birth. The day of birth counts as zero, so is the days elapsed.
Milestones such as the hundredth day are counted with the day of birth as day one. The hundredth day therefore falls 99 days after the birth.
Since the days-since-birth figure treats the birth as day zero, the two counts differ by one for the same date. It is an easy pair to confuse.
A child born on 1 April 2026 is 117 days old on 27 July 2026. The hundredth day is 9 July 2026 and the thousandth is 25 December 2028.
April contributes its remaining 29 days, May 31 and June 30, which comes to 90, and the 27 days of July bring the total to 117.
The okuizome ceremony is held on the 110th or the 120th day in some parts of Japan. Follow local custom for the date itself.
The reference date must not fall before the birth.