[thatthatis]

5 years is not a long time for information to be retrievable.

By comparison, my current version of office easily allows saving (not just opening, but saving) in versions compatible with office '97. That's ~17 years of saving backward compatibility.

[yuhong]

I think you can even save in Excel 5.0/95 format in current versions of Excel.

[bananas]

You can open wordperfect 5.1 (1989) in Office 2013 no problems.

Numbers can't even open ODS files at all, destroys iWork 09 documents and pretty much sticks a fork in most xslx documents.