Excel suddenly adding days and years!

[Seth Hill]

In an Excel spreadsheet which I have used for several years, something
strange suddenly happened. When I copy a date (such as 03/18/2001) from one
cell to another, Excel adds one day to the date and 4 years to the year (so
the copy is 03/19/2005). This just started happening today. I closed the
program, restarted the computer.
Any suggestions?

 

[Seth Hill]

I found the answer in another thread!

If you select Excel in the top menu, then Preferences, then Calculation, you
can select or unselect "Use the 1904 date system." Select it, unselect, and
all your dates change by 4 years and a day! Yes, they do.

I hope this is embarrassing to Microsoft. It should be. I hope NASA, or
the US Government, is not using Excel to calculate spaceship launches, or the
budget, etc. Because we might miss Mars by 4 years and a day, or balance the
budget 4 years and a day late. Scientists are puzzled...