Date & Time calculators
Plan dates and understand elapsed time with calendar-aware calculations.
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Pick the task that matches the answer you need.
Age Calculator
Find completed years, months and days on any selected date.
Date & TimeDate Difference Calculator
Count elapsed days or days until a selected future date.
Date & TimeDate Calculator
Add or subtract days, weeks, months or years from a date.
Date & TimeBusiness Days Calculator
Count Monday-to-Friday days between dates, excluding entered holidays.
Date & TimeTime Duration Calculator
Find elapsed days, hours and minutes between two UTC timestamps.
Date & TimeTime Zone Converter
Convert a local date and time between IANA zones, including DST overlaps and gaps.
Date & TimeWhat these calculators cover
Calendar questions look simple until a month has 28 days, a year has a leap day, or a clock jumps for daylight saving. These tools compare calendar dates at midnight UTC, so a daylight-saving change never adds or removes a day from a count.
Start with the shape of your question. If you know two dates, you need a difference. If you know one date and an amount of time, you need date arithmetic. If a time of day matters, use the duration or time zone tools, which work with timestamps rather than whole days.
Which tool fits your question?
Choose Age when you know a birth date and need completed calendar years, months and days on a selected date. Its next-birthday result follows the calculator's stated February 29 convention, which may differ from an official rule.
Choose Date Difference when you have two dates and need elapsed days, whole weeks or an inclusive count. It compares calendar dates at midnight UTC, so a daylight-saving clock change does not change the day count. For legal or institutional deadlines, check whether both endpoints count.
Date moves one starting date by a chosen number of calendar units and clamps missing month-end dates. Business Days counts Monday-to-Friday dates after a start date through an end date, removing only holidays you supply. Time Duration subtracts two UTC timestamps. Time Zone instead resolves a local clock reading using IANA rules, asking you to choose between two UTC instants during a repeated hour.
Each tool shows its formula, a worked example and the limits of its result. Read our calculation methodology for the shared rules.
Date & Time questions
01Which tool counts the days until an event?
Date Difference. Set the start to today and the end to the event date. The main count excludes today; the inclusive count adds one if you want both dates on the list.
02Why does adding one month to 31 January give 28 or 29 February?
February has no 31st, so Date Calculator clamps the result to the last day of the shorter month. Some contracts use a different month-end rule, so check the document when a deadline matters.
03Do business-day counts include public holidays?
Only the holidays you enter. Business Days removes Saturdays and Sundays automatically, but holiday calendars differ by country, province and employer, so the tool does not guess them.
04When should I use Time Zone Converter instead of Time Duration?
Use Time Zone Converter when a local clock reading has to be placed in another region. Use Time Duration when you already have two timestamps and need the time between them.