Free Date & Time Calculators
20 free online date and time calculators for age, date differences, business days, week numbers, time zones, timesheets, countdowns and Unix timestamps. Every tool correctly handles leap years, month lengths and timezone-aware conversions — running entirely in your browser.
About date and time calculators
Date and time calculations look simple until leap years, month-end rules, timezone offsets and daylight-saving transitions enter the picture. Every date tool on this page uses the IANA timezone database and handles those edge cases correctly, so the answer you get matches what a real calendar would produce.
Whether you are calculating your exact age, planning a project timeline, splitting a weekly timesheet or converting a Unix timestamp into a readable date, you will find a tool here that shows its work — every calculator displays the date arithmetic step-by-step, so you can trace how the result was produced.
Age & Date Differences
Calculate exact age, differences between two dates, or count elapsed days.
Age Calculator
Find your exact age in years, months, weeks and days.
Date Difference Calculator
Calculate the duration between two dates in multiple units.
Days Between Dates Calculator
Find the exact number of days between two calendar dates.
Day Counter
Count days between any two dates including or excluding endpoints.
Time Duration Between Dates
Compute duration in years, months, days, hours and minutes.
Day of the Week Calculator
Find which day of the week any historical or future date fell on.
Add & Subtract Dates and Times
Move forward or backward in time by days, weeks, months, hours or minutes.
Date Calculator
Add or subtract days, weeks, months and years from a date.
Time Calculator
Add or subtract hours, minutes and seconds.
Time Duration Calculator
Compute elapsed time between two clock times.
Hours Calculator
Convert between hours, minutes, seconds and decimal hours.
Countdown Calculator
Count down days, hours and minutes to any future event.
Birthday Countdown Calculator
See how many days until your next birthday.
Business Days & Work Hours
Timesheets, working days, overtime hours and week numbers.
Business Days Calculator
Count working days excluding weekends and custom holidays.
Work Hours Calculator
Calculate total hours worked from start, end and break times.
Timesheet Calculator
Total weekly timesheet hours and estimated pay.
Overtime Hours Calculator
Split regular and overtime hours from weekly work totals.
Week Number Calculator
Find the ISO week number for any date.
Time Zones & Technical Tools
Convert between time zones, Unix timestamps and check leap years.
Related Guides
Understand the calendar maths behind these tools.
Date & Time Calculator FAQs
Yes. The age calculator correctly handles leap years, month lengths and month-end edge cases such as being born on 29 February.
Business days exclude Saturdays and Sundays. You can optionally add custom holiday dates to further refine the count.
The time zone converter uses the IANA time zone database so it works with any city or region your browser recognises, including daylight-saving transitions.
Yes. Adding one month to 31 January produces 28 February (or 29 in leap years) using standard calendar rules, and adding a year to 29 February produces 28 February in non-leap years.
A Unix timestamp is the number of seconds that have elapsed since 1 January 1970 at 00:00:00 UTC. It is widely used in programming and databases to represent points in time unambiguously across time zones.
Explore Other Categories
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