There is a special place in hell for people who use 1904 date mode in Excel.

What the fucking fuck

Its because of fucking Mac.

Old Mac versions of Excel default to this mode. Normally, the base date for date calculations is January 0,1900. Dates are converted from integers, 0 being January 0,1900. However, using the 1904 system, 0 = January 1, 1904. Something about this being easier to handle leap years.

In any case, we use a Java program in Linux to convert Excel files into CSVs for data loading. This is the first time I've run into this issue in the 2.5 years I've been doing this. All the dates in this file I was attempting to load were exactly 4 years and a day off when I turned them into CSVs. Caused a little bit of confusion and chaos. And now we need to update our converter program for this new scenario. Fingers crossed it won't take all day.

SHOUT OUT: Thanks to my co-worker, @JustThat, for actually figuring out what was causing this.

INFO ON ISSUE: https://alandix.com/code2/...

You could remove "1904 date mode in" from your post.