Show weekday names

Suggestion received from a user:

> I'd like to suggest some improvement for this application: display the name of the day in the calendar.
This would help preventing misleading info, for instance when the initial letters of the month are the same as the initial letters of a day: MAR.
Reading too quickly makes people think that the proposal is on a "Mardi".
I just had the case several times in a row.
Moreover, knowing what day is what date would greatly help in general (see illustration).
> 

Obviously we wouldn't want it in red, but showing the name of the week day sounds like a good suggestion

Start by locating the calendar UI described in the issue and review the attached illustration for the intended placement and presentation. Add weekday names alongside the existing date information, avoiding red styling, and verify that dates are unambiguous across the calendar view.

Written by the indexing model from the issue text.