Is there any differences in the file format saved by different LibreOffice releases?

It is noticed that LibreOffice got releases frequently, I would like to know if these different releases affect the “format” of a *.xls file saved by LibreOffice Cals?

As I will develop a program that will read the data from a *.xls worksheet template created by LibreOffice Cals, I just would like to know if there are tiny differences in the format of *.xls documents saved by different releases of LibreOffice Cals.
Any difference may affect the performance of the program.

.xls are not native, which means, you calc find its a foreign language, it translate it into native while processing and then translate it back if you still want .xls.

Hi Anonymous,

Any tweak to our XLS import or export filters can affect the way that we process and write out our XLS files. For the specifics on what has changed, I believe that this code lives under filter/source/: