Convert Excel's serial date numbers (e.g. 45292) to real dates and back. Decimal fractions are converted to time of day.
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Files made in old Mac versions of Excel, or with “Use 1904 date system” turned on in Excel’s options, use the 1904 system. If dates are off by about 4 years (1,462 days), switch to it.
Copy a column from Excel and paste it here to convert every line. Numbers become dates, and dates (2024-01-01, 1/1/2024 as month/day/year, January 1, 2024, 20240101 and so on) become serial numbers. Several columns pasted together keep their layout.
Excel stores dates internally as a running count of days where January 1, 1900 = 1; if a cell's format is set to Number you see this raw count instead of a date. The fractional part is the time of day (0.5 = noon). Excel also famously treats the non-existent date February 29, 1900 as serial 60 — this tool accounts for that quirk, flags serial 60 explicitly, and converts everything from March 1, 1900 onward correctly.
Formulas you’ll often need when working with serial dates in a cell (for example, A1). Use "Copy" to copy a formula and paste it into Excel.
| What you want | Formula | |
|---|---|---|
| Turn a serial date into date text | =TEXT(A1,"yyyy-mm-dd") | |
| Include the time | =TEXT(A1,"yyyy-mm-dd hh:mm:ss") | |
| Turn date text into a serial date | =DATEVALUE("2024-01-01") | |
| Build a serial date from year, month and day | =DATE(2024,1,1) | |
| Today as a serial date | =TODAY() | |
| The current date and time | =NOW() | |
| Keep only the date part | =INT(A1) | |
| Keep only the time part | =MOD(A1,1) | |
| Convert a 1904-system value to the 1900 system | =A1+1462 | |
| Convert to a Unix timestamp (seconds) | =(A1-25569)*86400 |
If a formula result shows as a plain number, change the cell format to Date or Time.