Excel Date Converter
Convert an Excel serial date (OADate) — days since 1899-12-30 — to a calendar date and Unix time.
UTC / GMT
Your local time
ISO 8601
Relative
Unix seconds
Unix milliseconds
Current time updating:
How it works
Conversion: unixDays = serial − 25569, where 25569 is the days between 1899-12-30 and 1970-01-01.
Enter a value to convert it to a human-readable date, or click Use current time. Conversion is two-way and runs entirely in your browser.
Frequently asked questions
Why 1899-12-30, not 1900-01-01?
Excel intentionally treats 1900 as a leap year (it was not) for Lotus 1-2-3 compatibility, so its serial dates effectively count from 1899-12-30.
What is an OADate?
The OLE Automation date — used by Excel and COM — is a floating-point day count where the integer part is the day and the fraction is the time of day.