Dought & clear - On which day is i’tikaaf?

Is it permissible to observe i'tikaaf at any time other than the last
ten days of Ramadaan?.
Praise be to Allaah.
Yes, it is permissible to observe i'tikaaf at any time, but the best
is to do so during the last ten days of Ramadaan, following the
example of the Messenger of Allaah(peace and blessings of Allaah be
upon him) and his companions (may Allaah be pleased with them). Itwas
narrated that the Prophet(peace and blessings of Allaah be upon him)
also observedi'tikaaf during Shawwaal in some years.
And Allaah is the Source of strength. May Allaah send blessings and
peace upon our Prophet Muhammad and upon his family and companions.