Add or subtract days from a date
Result
Mon, February 8, 2027
100 days after Sat, October 31, 2026
The first day is not counted (the way Japan's Civil Code counts periods).
How it is calculated
The number of days is the end date minus the start date. Under article 140 of Japan’s Civil Code, the first day of a period counted in days is not counted unless the period starts at midnight, and that is the default here. With “Count the first day”, the start date counts as day 1.
Business days exclude Saturdays, Sundays, and the national holidays and other days off in the Cabinet Office holiday list, including substitute holidays and days between two holidays. For years the list does not cover yet, holidays are estimated from the Act on National Holidays and the special laws for imperial ceremonies, with the equinox days taken from the National Astronomical Observatory of Japan’s solar terms. This estimate matches the Cabinet Office list on every day from 1955 to 2027.
Year-end closures are not national holidays. Banks close from December 31 to January 3 under the Banking Act Enforcement Order article 5, and government offices from December 29 to January 3 under the Act on Holidays of Administrative Organs article 1.
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FAQ
What does "Count the first day" mean?
The start date counts as day 1. From January 1 to January 3 is 2 days without the first day and 3 days with it. Contract and legal periods in Japan normally leave out the first day unless the period starts at midnight (Civil Code article 140).
Which days are not business days?
Saturdays, Sundays, and the national holidays and other days off published by the Cabinet Office, including substitute holidays. If you choose a year-end closure, those days are left out too. Company-specific days off are not included.
Does it include holidays in future years?
Yes. For years the Cabinet Office has not announced, holidays are estimated from Japan's holiday law and the National Astronomical Observatory's equinox data, and the result says so. The equinox holidays become official each February for the following year, when the observatory's almanac is published in the Official Gazette.