Why 1899 12 30?

Microsoft chose to use the Lotus date format for Excel, for compatibility, but “fixed” this bug by moving “day one” back one day. Therefore day zero is 30 December 1899.

What is OA date format?

An OLE Automation date is implemented as a floating-point number whose integral component is the number of days before or after midnight, 30 December 1899, and whose fractional component represents the time on that day divided by 24.

How does excel handle dates before 1900?

If your date is after 1900, Excel automatically converts the date to a date serial number. If the date is before 1900, Excel stores the date as text. If the cell contains a real date, you want to add 1,000 years. An easy way to do this is to use the EDATE function and add 12,000 months to the date.

How does excel store dates?

Excel stores dates as sequential serial numbers so that they can be used in calculations. By default, January 1, 1900 is serial number 1, and January 1, 2008 is serial number 39448 because it is 39,447 days after January 1, 1900. Most functions automatically convert date values to serial numbers.

How do I fix 1900 dates in Excel?

To set the date system for a workbook in Microsoft Office Excel 2003 and in earlier versions of Excel, follow these steps:

  1. Open or switch to the workbook.
  2. On the Tools menu, click Options.
  3. Click the Calculation tab.
  4. To use the 1900 date system in the workbook, click to clear the 1904 date system check box.
  5. Click OK.

How do I change from 1900 to 2000 in Excel?

To change the century cutoff date, follow these steps:

  1. Click Start, point to Settings, and then click Control Panel.
  2. Double-click the Regional Settings icon.
  3. Click the Date tab.
  4. In the When a two digit year is entered, interpret a year between box, type the cutoff year that you want, and then click OK.

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