I've tried to resurrect bug 31149 but finally realised that this code is no longer needed. I think it's coming from the introduction of Masikto by bug 33703.
Created attachment 188204 [details] [review] Bug 41061: Remove unused calendar JS functions Since the introduction of Maskito by bug 33703 we do no longer need to valid dates when the flatpickr widget is closed. This patch removes the following JS function from staff and OPAC: * is_valid_date * validate_date * get_dateformat_str Test plan: 0. Do not apply this patch and confirm that the date string received by those functions has already been correctly formatted 1. Apply the patch and git grep to make sure no occurrence exists in the code 2. Confirm that you are still able to select dates with flatpickr