[Wiki Loves Monuments] Calendar WLM 2013

[Platonides]

It may be a bit hard to determine the day of the week.

You have a list of numbers:
 1 2 3 4 5 | 6 7 8 9 10 11 12 | 13 14 15 16 17 ...

So -knowing that the pipe splits Sunday from Monday- you have to go back
from that to find out that the 1st of May is actually Wednesday.

We could prepend a couple of empty squares, or simply put the days of
the previous month, ie. 29 30 1 2 3 4 5 | 6 7 8 9 10 11 12 | 13 14 15 16
17 ...