Steps to reproduce it:
- Create a site and a page, and add the search portlet to the page.
- Select Spanish as language in the Display Settings of the current user.
- Try to search "asdf".
- Over the result list, try to filter by date range. Selecting start and end date.
- Click on search.
- Over the result list, try to filter by date range
You will notice that the "date From" has been decreased in one day and the "date To" is also decreased in one day from the selected dates in the first search.
I guess that we are generating the dates using JVM methods (like new Calendar) without the user locale.