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 worked 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
How to choose a date & time calculator
Calendar dates or elapsed time?
A date difference counts calendar boundaries; elapsed hours compare instants. Choose the date tool for days between events, the age tool for completed years and months, and the hours tool for shifts or timesheets. Decide whether to include the first or last day. For a deadline, choose working days and supply the weekend pattern and holidays that apply to your organization. A holiday calendar from another region can produce a plausible but incorrect due date.
Use the event's date and time zone
Clock readings can repeat or disappear when daylight-saving time changes. Enter the actual dates and named time zone when you need elapsed time across such a change. A fixed UTC offset describes one offset, not a region's seasonal rules. Unix timestamps represent instants; confirm whether your source counts seconds or milliseconds. For recurring meetings, compare more than one date because different regions change their clocks on different schedules.
Hours across clock changes · Meeting planner · Unix timestamps