Free Online Date and Time Tools
Unix timestamps in both directions, timezone conversion, days between two dates, business days with weekends excluded, countdowns, week numbers. Date arithmetic is where quiet bugs live: months are different lengths, most timezones shift twice a year, and ISO week 1 is not always the week containing January 1. These show the intermediate values as well as the answer, so you can check the result instead of trusting it.
Tools in this category
- Business Days Calculator Count the number of business days (working days) between two dates. Skips weekends, lets you exclude your own holidays, and shows weekend days, holidays, and total calendar days — all in your browser.
- Days Between Dates Calculator Count the number of days between two dates. Get the total number of calendar days, the gap in weeks, weekday and weekend days, and a weeks-and-days breakdown — all instantly in your browser.
- Months Between Dates Calculator Calculate how many months are between two dates. Get the whole months and leftover days, the exact number of months as a decimal, a years-and-months breakdown, plus total weeks and days — instantly in your browser.
- Years Between Dates Calculator Calculate how many years are between two dates. Get the whole years plus leftover months and days, the exact number of years as a decimal, a years, months and days breakdown, and the totals in months and days — instantly in your browser.
- Birthday Countdown A live countdown to your next birthday in days, hours, minutes, and seconds, plus the exact birthday date, the day of the week it falls on, and the age you will turn.
- Time Zone Converter Convert a date and time from one time zone to another. Pick a source and target zone to see the converted time, the UTC offsets, the difference between zones, and whether the result lands on the same, next, or previous day.
- World Clock See the current time in cities around the world at a glance. The World Clock shows live, ticking clocks for multiple time zones at once, with each location's date, UTC offset, and a day or night indicator. Add or remove cities and switch between 24-hour and 12-hour formats.
- UTC Converter Convert your local time to UTC, or UTC back to your local time, in one click. Enter a date and time and instantly get the Coordinated Universal Time equivalent along with the ISO 8601 timestamp, the Unix epoch in seconds, and your time zone's current UTC offset. Daylight saving is handled automatically using your device's own time zone data.
- ISO 8601 Date Converter Parse, validate, and convert any ISO 8601 date or timestamp. Paste an extended timestamp like 2026-06-19T14:30:00Z, a week date like 2026-W25-5, an ordinal date like 2026-170, or a basic format with a timezone offset, and instantly see whether it is valid plus its human-readable form, UTC ISO 8601, Unix epoch in seconds and milliseconds, day of week, week date, ordinal date, RFC 1123 string, and how long ago or away it is. Everything runs in your browser.
- Leap Year Checker Check whether any year is a leap year. Enter a year like 2024 or 2100, or use the current year, and instantly see if it is a leap year, why (the divisible-by-4, century, and divisible-by-400 rules), how many days that year has, whether February has 28 or 29 days, plus the previous and next leap years and the upcoming leap years. Everything runs in your browser.
- Week Number Calculator Find the ISO 8601 week number for any date, and look up which dates fall in a given week. Pick a date (or use today) to see its ISO week number, the week-numbering year, the week's Monday start and Sunday end dates, the weekday, the day-of-year, how many weeks the year has, and how many weeks are left in the year. Reverse it too: enter a year and week number to get that week's date range. Everything runs in your browser.
- Countdown Timer A free online countdown timer that ticks down live in your browser. Set hours, minutes, and seconds — or tap a preset like 5, 10, or 25 minutes — then start, pause, resume, and reset whenever you like. When the timer reaches zero it flashes and plays an optional alert sound. Nothing is installed and nothing is uploaded; it all runs locally.
- Stopwatch A free online stopwatch that counts up live in your browser with hundredths-of-a-second precision. Press start to begin timing, pause and resume without losing your place, record lap and split times, and reset whenever you like. Nothing is installed and nothing is uploaded — the stopwatch runs entirely on your device.