Problem with excel dates

Hello! the issues is that we have to copy and paste a date from a report to add it in to another report and the date change the format. We have tried everything and we are not sure what might be happening. One thing is that we work in Spain and our colleagues in Sweden, not sure if this is making excel go crazy...

I would like to explain with some images.

This is how it looks:

This is how we want it

I write it like this in the cell

And when I press enter it changes to this

The format appears as this:

But it should appears as this:

If we just change the category to "General" , then in Sample it appears like this:

And once we confirm it it appears 45513 as numbers in the cell 😄

Anyone can give us a idea how to solve this issue? 

Thanks!