Excel Date Serial Number Converter
Type serial numbers or dates, one on each line, to convert between them. Choose the 1900 or the 1904 date system and see the weekday for each date.
Worked examples
Serial to date
45000
2023-03-15 (Wednesday)
1900 date system. The decimal 45000.5 adds 12:00:00.
Date to serial
01/01/2000
36526
Day first. 1 January 2000 is serial 36526 in the 1900 system.
The 1904 system
43100 with the 1904 system
2022-01-01
In the 1900 system the same date is 44562, which is 1,462 more.
About Excel Date Serial Number Converter
A spreadsheet stores a date as a number: the count of days since a starting date, with the time of day as a fraction. In the usual 1900 system, serial 1 is 1 January 1900, serial 45000 is 15 March 2023 and 45000.5 is midday on that day. Data exported without date formatting shows these raw numbers, and so do dates read by some scripts. This converter turns them back into dates, and dates into serial numbers.
Type a number or a date on each line and pick the date system. The 1900 system has a well known fault kept for old files: it treats 1900 as a leap year, so serial 60 is a 29 February 1900 that never existed. Some older workbooks use the 1904 system, where serial 0 is 1 January 1904, so the same number gives a date 1,462 days later than in the 1900 system. Each result also shows the day of the week.
How to use Excel Date Serial Number Converter
- Type serial numbers or dates, one on each line.
- Choose the 1900 date system, or 1904 for some older workbooks.
- If your dates are numbers like 03/04/2024, choose day first or month first.
- Read the results and copy what you need.
Common uses
- Making sense of a column of five digit numbers in an export
- Checking a date a script read from a workbook
- Turning a list of dates into serial numbers for a formula
- Finding the time of day held in a decimal
Frequently asked questions
What date is serial 45000?
15 March 2023, a Wednesday, in the 1900 system. 45658 is 1 January 2025.
What does the decimal part mean?
The time of day as a fraction of 24 hours. 0.5 is noon, 0.25 is 6 am and 0.75 is 6 pm. So 45000.75 is 6 pm on 15 March 2023.
Why are my dates four years out?
The workbook probably uses the other date system. The 1904 system counts from 1 January 1904, so a serial number is 1,462 days smaller for the same date. Switch the date system and compare.
What is wrong with 29 February 1900?
Nothing in the real calendar, because 1900 was not a leap year and the day did not exist. The 1900 system includes it to stay compatible with an early program. Dates before 1 March 1900 are therefore one day out against the real calendar.
Can serial numbers be negative?
Not in a spreadsheet date. Numbers below 1 are shown as times with no date, and negative numbers cannot be shown as dates at all.