About Daycount
Daycount is a free date calculator. It counts the days between two dates, counts down to a date, adds or subtracts days, weeks, months and years, counts business days, finds a date a number of business days away, and works out exact age, anniversaries, the day of the week, ISO week numbers, the time between two moments and the public holidays of a year. There's no sign-up, and the dates you enter are never sent to a server.
Who makes it
Daycount is made and run by Lumen Lab, a one-person software studio that also makes Owlight, a Mac menu bar app, and SetNote, a workout log web app. The Korean edition of this site is called 며칠 계산기.
How it calculates
- Days between dates: the later date minus the earlier one. Turn on “Include start date” to count the first day too.
- Months: counted from date to date. If the month is too short, its last day is used, so January 31 plus one month is February 28 (29 in a leap year).
- Age: whole years since the last birthday, then months and days. People born on February 29 have their birthday on February 28 in other years.
- Business days: Saturdays, Sundays and the holidays of the selected calendar (US federal holidays or Korean public holidays) are skipped, on the days they are observed. When finding a date N business days away, the starting day isn't counted.
- Week numbers: ISO 8601. Weeks start on Monday, and week 1 contains the year's first Thursday.
Holiday data and accuracy
US federal holidays and Korean public holidays for 2015 to 2035 come from the open-source holidays library. Outside those years only weekends are skipped, and the calculator shows a warning. One-off closures announced later, such as extra days off given by executive order, are not included.
The date logic is checked by automated tests against more than 3,200 answers computed separately in Python (datetime, dateutil and the holidays library). Results are for planning. For legal deadlines, contracts or payroll, confirm the rule with the organization involved.
Advertising
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Contact
Found a wrong result or a missing holiday, or want a feature? Email woxocoso@gmail.com.