Date Calculator & Unix Timestamp
Convert Unix timestamps, count days and business days between dates, and add or subtract time
- Files never leave your device
- Runs in your browser
- Free, no sign-up, no watermark
Unix timestamp converter
Current Unix time
— ms
Date difference
Add or subtract time
Month ends are clamped, the way Day.js and Moment do it: Jan 31 + 1 month = Feb 28 (29 in leap years).
Date information
Age calculator
How to use Date Calculator & Unix Timestamp
Convert Unix timestamps in seconds, milliseconds, microseconds or nanoseconds to readable dates, and back. The same page counts the days and working days between two dates, adds or subtracts time, and lists the week number, quarter and other facts for any date. Everything runs in your browser.
- 1
Paste a timestamp or date into Timestamp or date, or click Use now; the unit is detected automatically unless you pick one under Unit.
- 2
Choose a Time zone in the side panel to see the local time there; dates typed without an offset are read in that zone.
- 3
Under Date difference, set Start date and End date (turn on Include time of day for hours) to get the gap and the number of working days.
- 4
Under Add or subtract time, enter amounts from years to seconds, choose + Add or − Subtract, and copy the Result.
- 5
Enter a date under Date information to see its weekday, ISO week, day of the year, quarter and whether it falls in a leap year.
Frequently asked questions
Is my timestamp in seconds or milliseconds?
With Unit set to Auto, numbers of up to 11 digits are read as seconds, 12–14 digits as milliseconds, 15–17 as microseconds and longer ones as nanoseconds. The note under the input says how it was read; choose s, ms, µs or ns to override it.
How are working days counted?
The start and end dates are both included. Saturday and Sunday are days off by default; change them under Days off each week, and list holidays one per line, such as 2026-12-25. Public holidays are not built in, extra working days on a weekend cannot be set, and your settings stay in this browser.
Why does January 31 plus one month give February 28?
The day is clamped to the last day of the target month, the same way Day.js and Moment do it. In a leap year the result is February 29.
Which time zone is used for a date without an offset?
The one selected under Time zone, which starts as your device’s zone. Input ending in Z or an offset such as +08:00 keeps that offset. To compare several cities at once, use the Time Zone Converter.
Can I format a timestamp my own way?
Yes. Type a pattern under Custom format using Moment / Day.js tokens such as YYYY-MM-DD HH:mm, or pick a preset from the list next to it. Text inside [brackets] is printed as typed.
Is anything sent to a server?
No. Calculations use your browser’s built-in calendar and time zone data, and nothing you type leaves your device.