Handling of time cells is not consistent for different readers

[stof]

When reading a time cell in an ODS file, a DateIntervalCell is used. When reading a XLSX file, a DateTimeCell is used (and I don't know which date it has).
This makes it hard to write code that can support both XLSX and ODS as it forces to handle different cell types (both for reading and for writing). It would be great to have a common abstraction between those readers and writers to make the code common.

[stof]

@Slamdunk is this something that is supposed to be abstracted properly ?

[Slamdunk]

I haven't dug this, sorry.

If you are able to reasoning of the topic & code and propose a comprehensive solution in a PR, I'd be glad to review and merge it 💪

[stof]

I don't have an idea right now but I'll try to think about it.