Cannot select a date on the right hand side 3 month mini calendar, after previously selecting one

After selecting a day on the right hand side 3 month calendar, you cannot select another day from there.
To reproduce:

1. go to https://moodle.org/calendar/view.php?view=day
2. on the right hand side "MONTHLY VIEW", in any month, click on a date which has an event
3. you should see in the centre page area the day and its event, (with a previous day and next day links). Ad you do see that.
4. on the right hand side "MONTHLY VIEW", in any month, click on a different date which has an event
5. I'd expect that you should see in the central area the newly selected date, and its event. But you do not. It stays on the previously selected date.

And that's the bug.