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# ETL: ExcelSerialToDate

> Convert an Excel serial date number (1900 date system) to a UTC datetime value. Use when ingesting spreadsheet exports that store dates as numbers.

## Description

Converts an Excel serial date number (1900 date system) to a datetime data type. The integer part is the number of days since 1899-12-30; the fractional part is the time of day. The result is in UTC.

Use this function when a source — typically a spreadsheet export — represents dates as numeric serial values instead of formatted date strings.

## Syntax

`ExcelSerialToDate(serial_number)`

## Arguments

* *serial\_number* - numeric value representing an Excel serial date. The integer part is the number of days since 1899-12-30; the fractional part is the time of day.

## Examples

* `ExcelSerialToDate(43831)` returns datetime value `2020-01-01T00:00:00Z`
* `ExcelSerialToDate(43831.5)` returns datetime value `2020-01-01T12:00:00Z`

## Return value datatype

datetime

## Impact of null value

If *serial\_number* is null, returns null.

## Related functions

* [DateToExcelSerial](/docs/etl/datetoexcelserial) — the inverse conversion.
* [ToDate](/docs/etl/todate) — parse datetime values from strings or Unix milliseconds.