Category documentation
Time & date: instructions and references
Dates become confusing when calendar rules, time zones and business conventions are mixed together. These tools state whether they use local device time, UTC-midnight calendar dates or a signed duration so you can choose the right interpretation.
Choosing a tool: Use a calendar-date tool when the question is about dates on a page, and a duration tool when elapsed clock time matters. For a deadline across time zones, convert the times explicitly before relying on a local-device result.
10 tool references, grouped by category. Searches stay in this tab.
Time & date
Browse category Time & date
Age CalculatorCounts completed calendar years, then separately calculates elapsed calendar days.Date DifferenceElapsed days = (end UTC midnight − start UTC midnight) ÷ 86,400,000.Add / Subtract DaysAdds a signed whole number of calendar days, rolling across month and year boundaries.Business Days CalculatorCounts Monday–Friday after the start date through the end date, subtracting unique supplied weekday holidays.Week NumberISO 8601 weeks start Monday.Day Of YearJanuary 1 is day 1.Leap Year CheckerA year is leap if divisible by 4, except centuries unless divisible by 400.Countdown CreatorSubtracts the current clock time from a target interpreted in the device’s timezone, updating each second.Duration CalculatorTotal seconds = hours × 3600 + minutes × 60 + seconds.Time Duration CalculatorSubtracts start clock minutes from end clock minutes; optionally wraps an earlier end into the next day.