Org-mode deadline calendar formatting

[wlmhgns]

The Org-mode calendar is bugged [M-x calendar]

Current date is Monday 31 Oct, a week in which October has two days.
The week is displayed at the end-bottom of the September calendar on a new row.

No month's formatting is correct as displayed.

[rougier]

Do you mean it is bugged when using nano-emacs? From your display, I can see you're using a proportional font and this might be the reason the calendar appears to be incorrect.