EpochLab

Excel Serial Date Converter

Read and write Excel serial numbers

The serial itself: what the whole part means, what the fraction means, and where the two date systems and the 1900 bug make the arithmetic stop being simple.

Questions people ask

The things that come up about excel serial date converters, answered plainly.

What does the decimal part mean?

Time of day as a fraction of 24 hours. 0.5 is noon, 0.75 is 18:00. So 45489.5 is midday on 16 July 2024 — which is also why subtracting two datetime cells and formatting the result as a number gives days with a fractional part.

What is serial 60?

Excel's 29 February 1900 — a date that never happened. Serials below it are one day out from what Excel displays, which is why dates in January and February 1900 cannot be converted reliably in either direction.

Related tools

Julian days, Excel serials, GPS time, cron expressions and format validators.

Excel Date ConverterA spreadsheet serial to a calendar date and back, in both the 1900 and 1904 systems — with the phantom leap day of 1900 flagged where it matters.
SQL Date FormatterOne instant, rendered as a literal for PostgreSQL, MySQL, SQL Server, Oracle, SQLite, BigQuery and Snowflake — plus how each spells 'now' and how each reads a Unix timestamp.
Epoch ConverterThe same conversion as a Unix timestamp, plus the other epochs a number might belong to — Windows FILETIME, .NET ticks, Excel serials, Julian days — ranked by how plausible each reading is.
Date ValidatorChecks that a date exists as well as parses — 31 February and 29 February in a common year both parse fine in most languages, and neither is a date.

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