What's the difference between a Unix timestamp in seconds and milliseconds?

A Unix timestamp in seconds is the integer count of seconds since 1970-01-01 UTC (10 digits for present-day values). Milliseconds is the same count × 1000 (13 digits). JavaScript's Date.now() returns milliseconds; most databases and the Unix date +%s command return seconds. Paste either into epoch-converter, it detects the format by digit count and converts both ways.

How do I calculate the exact number of days between two dates?

Paste both dates into find-date-difference. The result shows days, weeks, months, and years in parallel, so a 90-day renewal clause and a 3-month clause can be compared side by side. For age-specific output (years + months + days), find-age-difference breaks the interval down the way legal forms want it.

How do I convert a time between two time zones?

Use convert-time-between-timezones when the input is an IANA zone ID like America/New_York or Asia/Tokyo, and convert-time-between-countries when it's a country name. Both handle DST automatically from the target date, a 3 PM New York meeting in July (EDT) and in January (EST) maps to different UTC offsets.

How do I check whether a year is a leap year?

A year is a leap year if it's divisible by 4, except century years, which must also be divisible by 400, so 2000 is a leap year, 1900 isn't. check-if-leap-year applies the Gregorian rule. find-leap-years lists every leap year in a given range, useful for generating test data or a 30-year calendar.

How do I convert military time to regular time?

Paste the 24-hour value into convert-military-time-to-regular-time. 1400 becomes 2:00 PM; 0030 becomes 12:30 AM. For the reverse direction, convert-regular-time-to-military-time takes 6:45 PM and returns 1845. Both accept input with or without the colon separator.

Can I find out what day of the week a historical date fell on?

Yes. find-day-of-week accepts any Gregorian date from year 1 onward and returns the weekday. For dates before the Gregorian calendar's 1582 adoption, the result is the proleptic Gregorian weekday, the calendar in use today, projected backward. Julian-calendar weekdays need a pass through convert-gregorian-date-to-julian-date first.

Date & Time Tools

Date and time tools convert between calendar formats, clock formats, and timestamps, Unix epoch, ISO-8601, 12-hour AM/PM, 24-hour military, Julian day, Gregorian date, plus time-zone math across 400+ IANA regions. A backend engineer debugging a webhook that ships epoch milliseconds to a service expecting ISO UTC can paste 1740000000 into epoch-converter, read the human date, then offset it for the receiver with timestamp-timezone-converter.

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All tools in this category

Add Fuzziness to Clock Time Generator →

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Calculate Time Zone Difference →

Check Common Year →

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Convert 12-Hour to 24-Hour Time →

Convert 24-Hour to 12-Hour Time →

Convert Cat Age to Human Years →

Convert Date to Julian Day →

Convert Days to Hours →

Convert Days to Months →

Convert Days to Weeks →

Convert Days to Years →

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Convert Gregorian Date to Julian Date →

Convert Hours to Days →

Convert Human Age to Cat Years →

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Convert Human Time to Unix Time →

Convert Julian Date to Gregorian Date →

Convert Julian Day to Date →

Convert Military Time to Regular Time →

Convert Months to Days →

Convert Regular Time to Military Time →

Convert Seconds to Time →

Convert Time Between Countries →

Convert Time Between Timezones →

Convert Time to Decimal →

Convert Time to Seconds →

Convert Unix Time to Human Time →

Convert Weeks to Days →

Convert Years to Days →

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Decrement Calendar Date →

Decrement Clock Time →

Draw Analog Clock →

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Find Common Years →

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Leap Year Finder →

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