Time & Date Calculator

Time & date calculations explained

Whether you are planning a project, booking travel, or checking payroll hours, a reliable date calculator and time calculator saves manual counting. This page combines four common workflows: measuring the gap between two calendar dates (days between dates), shifting a deadline with add days to date (or subtracting months and years), measuring a same-day or overnight time duration, and translating clock times with a time zone converter using IANA regions (so daylight saving is reflected for the date you pick).

Date difference calculator

The date difference calculator reports a calendar breakdown (years, months, and days) from the earlier date to the later date, plus total days, decimal total weeks, and total hours (24 hours per calendar day). If your end date is before the start date, we still show the same span and note the reversed order so you can interpret signed schedules easily.

Add or subtract from a date

Use negative numbers to subtract. Months and years follow the calendar (e.g. adding one month to 31 January moves to February’s last day when needed). Hours adjust the local clock after the calendar shift.

Hours calculator & duration

The hours calculator mode is ideal for shifts and timers: enter start and end clock times and read hours, minutes, seconds, plus totals expressed purely in hours, minutes, or seconds.

Time zone converter

Choose regions such as EST, CST, PST, IST, JST, AEST, CET, China CST, SGT, GST, NZST, BST, UTC, and GMT. Always set the date when converting near DST changes for an accurate instant.

• Private: all math runs in your browser
• Four modes: difference, add/subtract, duration, time zones
• SEO-friendly labels: time calculator, date calculator, days between dates, add days to date
• Works on desktop and mobile with the same modern layout