1900 v 1904 date systems

[JenniferMurphy]

I was working on a sheet to compare actual vs expected times (0-60 minutes) when I ran into a problem with negative time differences. If the difference between the expected and actual items was positive (non-negative), no problem, but if it was negative, the cell, which was formatted as "+h:mm;-h:mm;=h:mm", was filled with # signs. No matter how wide I made that cell, it still showed "#################". This only happens if it is formatted as time. If it is formatted as a number, it correctly shows the negative value. What's up with that?

One website said I need to switch to the 1904 date system. I tried that and it fixed the problem with the negative times. But I'm wondering what else it involves. What other gotchas does M$FT have in store for me?

I did a little more testing and reading.

It appears that the setting applies to the entire workbook (all sheets), but not to other workbooks. Is that correct? If I change one workbook, that will not affect any others. On the other hand, if I want to switch over to the 1904 system completely, I will have to change each of my hundreds of workbooks one at a time. Right?

Several websites said that there can be some compatibility issues, but it seemed that it was mostly in sharing data. I rarely share any of my workbooks with others or even import data from others. Can I still run into a problem in that area?

Can I run into problems if I change an existing workbook with existing date data from one system to another? I switched a couple back and forth and it didn't seem to change any of the output.

Is there anything else I should be aware of?

Should I switch over to the 1904 system for everything? I doubt I will have to deal with dates before 1904.

 

[mole999]

all dates between different work books will be out by four years, a 1000 in one will be different to another where applied. when I have used it I choose to put that on a sheet to demonstrate that this book has a difference, you might add it to the file name. Really becomes an issue if you share books with others. In the book isn't an issue

 

[RoryA]

Any existing dates will adjust to display differently, though the underlying number value will remain the same.