Date and time calculators
Days between dates, exact age, business days, time zones with daylight-saving rules, Unix timestamps, ISO week numbers, calendar conversions and sunrise and sunset times.
15 calculators · 87 checked examples
Find the right calculation
- Hours worked when the clocks change
Use dates and a time zone to distinguish clock readings from elapsed time, including repeated hours and unpaid breaks.
- A deadline that skips weekends and holidays
Add or subtract working days, choose the weekend pattern and supply the holidays that apply to your calendar.
- A meeting that works across time zones
Convert the meeting's actual date and compare working-hour overlaps, including seasonal changes in the time difference.
Dates
- Add or subtract days from a date
The date a number of days, weeks, months, years or business days after or before a start date, with its weekday and the calendar days moved.
- Age calculator
Exact age from a date of birth in years, months and days on any date, with the next birthday and age in months, weeks, days and hours.
- Days between dates calculator
Days between two dates, also as years, months and days, weeks and hours, plus business days after weekends and your own holidays.
- Business days calculator: add working days to a date
The deadline N business days after or before a start date, skipping weekends and the holidays you list, with the calendar days it spans.
Time
- Countdown calculator: time until a date
Countdown to a date: days, hours, minutes and seconds until (or since) a date and time in any time zone, ticking live and allowing for clock changes.
- Hours calculator: hours between two times and weekly timesheet
Calculate work hours, breaks and weekly timesheets. Use dates and a time zone for overnight shifts across daylight-saving changes and repeated hours.
- Military time converter (24-hour time)
Military time converter: 12-hour to 24-hour time and back, how it is spoken, time-zone letters with the Zulu equivalent, and a full-day chart.
- Time zone converter and meeting planner
Time zone converter: turn a time in one zone into local time in up to 12 others, with daylight-saving changes applied and a meeting planner grid.
- Unix timestamp converter
Unix timestamp converter: epoch seconds, milliseconds, microseconds or nanoseconds to an ISO 8601 UTC date and local time, and dates back to epoch time.
- Time calculator: add and subtract hours and minutes
Add and subtract hours, minutes and seconds from a list of durations, with the total as H:MM:SS, decimal hours, minutes and seconds.
Calendar
- Calendar converter (Hijri, Hebrew, Persian, Julian)
Convert a Gregorian date to Hijri (Umm al-Qura and tabular), Hebrew, Persian, Indian national (Saka) and Julian dates, or a Julian date back.
- Day of the week calculator
Day of the week for any date, past or future: the weekday in the Gregorian calendar, worked through step by step with Zeller's congruence.
- Leap year checker
Leap year checker: whether a year has 366 days under the Gregorian rule, which test decides it, and the previous and next leap years.
- Week number and day of year
Week number for any date: ISO 8601 week and week-numbering year, US week number, day of the year, days left in the year and the quarter.
Sun & sky
Choosing a calculator: Date & time
How do I count the days between two dates?
Use the date difference calculator, which counts the calendar days between two events. Decide first whether to include the first or last day, because that changes the count by one.
How do I calculate a deadline in working days?
Use the working-days deadline calculator and enter the weekend pattern and holidays that apply to your organization. A holiday calendar from another region can give a plausible but wrong due date.
How do I find an exact age?
The age calculator gives the exact age in years, months and days on any date, with the next birthday. For hours worked in shifts or on a timesheet, use the hours calculator instead.
How do I convert a time between time zones?
Use the time zone converter with named time zones rather than fixed UTC offsets, because an offset does not follow a region's daylight-saving changes. For a recurring meeting, check more than one date, since regions change their clocks on different days.