Excel Date Converter
Convert Excel serial numbers to dates and times, or encode a workbook date, using the 1900 or 1904 date system.
Starts with an editable example. Replace the dates and rules with your own.
Your calculation
Ready when you are
Choose your dates.
Select your counting rules and calculate.
Calculation details
| Step | Value |
|---|
How to use this calculator
Select the workbook system and conversion direction. Paste serial values or enter a floating date/time with optional milliseconds.
Excel serials do not assign a time zone. Serial 60 in the 1900 system represents the fictional February 29, 1900 and is reported explicitly. Negative serials are unsupported; output calendar precision is milliseconds.
A worked example
In the 1900 system, serial 25569.5 is January 1, 1970 at 12:00. Serial 61 is March 1, 1900.
Why is my result about four years off?
Check the workbook date system. The 1900 and 1904 systems differ by 1,462 serial days for dates supported by both.
Which calendar and years are supported?
Each result states its calendar, time scale, precision and supported range. Batch converters accept up to 100 nonempty input lines and retain invalid rows. Copy, CSV and print include the calculation rules. Calendar downloads appear when a result contains dated events. Calculations run in your browser; no reminders or jobs are scheduled.
What happens to my dates?
Calculations run on your device. Saving a calculation is optional and keeps it in this browser. A setup link contains the dates and settings you entered; anyone with the link can read them. Use one tab per saved calculator. Clear saved data from Privacy & settings.