Date conversion & calculation
Turn numeric timestamps into readable dates, and dates into milliseconds.
How to useCalendar · Lunar dates · Holidays
Browse months and use a selected date in the calculators.
UK: bank holidays for the selected region. Canada: original dates of 10 holidays under federal jurisdiction; provincial holidays and workplace-specific substitute days are not included.
Select a date for details. Use arrow keys to move between dates and Enter to select.
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This month's holidays for selected countries
Coverage and data sources
Calendar and Korean lunar dates: 1900–2050. Holiday coverage years: 2026, 2027. Data date: 2026-09-16.
The data date is the oldest review/update date across included country/year datasets. US dates use federal rules; Canadian dates use rules after checking the official federal holiday list. Special closures and changes in law are not automatically incorporated.
South Korea and Japan: national holidays. US: federal holidays and observed dates. UK: dates as published in the official bank holiday list; when a substitute is listed, the original commemorative date may not appear separately. Canadian federal holidays do not mean days off for all workers nationwide. School/workplace closures and holiday-excluding day counts are not supported.
Holiday data is bundled with the site and is not updated automatically. Special holidays and policy changes require a data update; check official announcements for important plans. Today uses your device's local date; holidays use each country's calendar dates.
Sources: Korean holiday sources · US OPM · Japan Cabinet Office · GOV.UK · Canada.ca · korean-lunar-calendar (MIT)
UK data: GOV.UK, Open Government Licence v3.0.
The calendar and lunar conversion run in your browser without external API requests.
Date and day calculator
Find your 100th day, add or subtract days, and count days between dates.
Find the Nth day
Day 1 is the base date. One day after is the next date.
Days between two dates
The same date gives 0 days, or 1 day when both endpoints are included.
Calendar dates are independent of time zones and daylight saving time. Weekends and holidays are included. Today uses your device's local date, independently of the timestamp time zone above.
One moment, different representations.
Unix timestamps measure time since January 1, 1970 at 00:00:00 UTC. This tool uses milliseconds. Negative values represent earlier times.
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Choose a direction
Convert a millisecond number to a date, or a date to milliseconds.
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Enter a time and time zone
Use YYYY-MM-DD HH:mm:ss.SSS. A trailing Z or an offset such as +09:00 takes precedence over the selected time zone.
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Compare or convert back
Compare KST, UTC, and milliseconds for the same instant. Use Reverse conversion to check the round trip.
1735689600123 milliseconds
UTC 2025-01-01 00:00:00.123
KST 2025-01-01 09:00:00.123These are the same instant in different zones. Multiply a seconds-based timestamp by 1,000 before entering it.
Frequently asked questions
Does it detect seconds versus milliseconds?
No automatic guessing: values always mean milliseconds. For example, 1000 is one second after the epoch and 0 is 1970-01-01 00:00:00 UTC.
What happens if I specify a time zone?
A trailing Z or ±HH:mm takes precedence. Otherwise, dates use the selected KST (+09:00) or UTC zone. KST is fixed at +09:00 and does not model historical time-zone changes.
What date range and precision are supported?
Years 0001–9999 in UTC, with millisecond precision. Invalid dates, leap seconds, and sub-millisecond input are rejected.