📆 Convert between Excel and JS dates

This script takes into consideration the Leap-Year bug and the date difference between 1900 and 1904 Excel Date Systems.

Usage

// You can verify these results with the example at:
// https://docs.microsoft.com/en-us/office/troubleshoot/excel/1900-and-1904-date-system

const toExcelDate = require('js-excel-date-convert').toExcelDate;
const fromExcelDate = require('js-excel-date-convert').fromExcelDate;

const jul = new Date('jul 5 1998');

toExcelDate(jul);  // 35981 (1900 date system)

toExcelDate(jul, true); // 34519 (1904 date system)

fromExcelDate(35981); // "Sun, 05 Jul 1998 00:00:00 GMT"

fromExcelDate(34519, true);  // "Sun, 05 Jul 1998 00:00:00 GMT"

API

fromExcelDate(excelDate, date1904): Date

Param	Type	Required	Description
excelDate	number	yes	An integer number representing a date in Excel.
date1904	boolean	no	Set this to true if the date is encoded in 1904 Date System. This is the default format for Excel in MacOS. If you're using SheetJS you can check which system the file is using by calling wb.Workbook.WBProps.date1904

toExcelDate(date, date1904): number

Param	Type	Required	Description
date	Date	yes	Date to encode into Excel format.
date1904	boolean	no	If true, the date will be encoded to 1904 Date System. This is the default format for Excel in MacOS. If you're using SheetJS you can check which system the file is using by calling wb.Workbook.WBProps.date1904

Credits

Raschid JF. Rafaelly

https://raschidjfr.dev