From 22/12/2017 to 7/01/2018,

from 23/03/2018 to 3/04/2018

summer holidays from 21/06/2018 to 13/09/2018.

There are some long weekend too (i.e from 6/12/2017 to 10/12/2017) but these are the longest holidays. 

on Wednesday, from 11.00 to 12.00,

on Thursday, from 10.00 to 11.00 and

on Friday, from 11 to 12.00.