Excel date converter
Spreadsheets store dates as numbers: whole days since a start date, with the time of day as a fraction. Enter a serial like 45000 to see the date, or type a date to get its serial number in the 1900 or the 1904 system.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Enter a serial number such as
45000, or a date such as 2023-03-15. A time may follow the date: 2023-03-15 18:00.
- Pick the date system your file uses. Windows Excel and Google Sheets use 1900.
- Read the result, and the equivalent serial in the other system.
How it works
Serial numbers from 61 on are days after 30 December 1899, so 45000 is 45 000 days after that date: 15 March 2023. Serials 1 to 59 (January and February 1900) are counted from 31 December 1899, because Excel’s serial 60 is the non-existent 29 February 1900. The decimal part of a serial is the fraction of a day: 0.75 is 18:00.
Worked examples
- 45000 is 15 March 2023, a Wednesday.
- 45000.75 is 15 March 2023 at 18:00.
- 1 is 1 January 1900, and 61 is 1 March 1900.
- 0 in the 1904 system is 1 January 1904.
Good to know
All times are shown as written, with no time zone. Spreadsheets do not store a zone with a date serial.
Frequently asked questions
What is an Excel serial date number?
It is the number of days since a start date, with the time of day as the decimal part. In the 1900 system, serial 1 is 1 January 1900 and 45000 is 15 March 2023. 0.5 is noon.
Why is 29 February 1900 in Excel?
Excel treats 1900 as a leap year, a bug inherited from Lotus 1-2-3 that was kept for compatibility. Serial 60 is that missing day, so serials 61 and above are a plain day count from 30 December 1899, while serials 1 to 59 are shifted by one day to leave room for it.
What is the difference between the 1900 and 1904 systems?
The 1904 system counts from 1 January 1904 as day 0 and has no phantom leap day. The same date has a serial 1 462 less in the 1904 system, so 45000 becomes 43538.
Does Google Sheets use the same numbers?
Google Sheets counts days from 30 December 1899 as day 0, which gives the same serial as Excel for every date from 1 March 1900 onward. Dates before that differ by one day.