Shalom, There is no specific time to learn about Tefilah, but since Tefila is one of the pillars the world is standing on (Torah, Avoda (Tefila) & Gemilut Chasadem (Charity)) and is considered one of the most important actions a Jew must do in his service to G-od, therefore it is highly recommended for anyone to learn about Tefila anytime during the year and even highly suggested to learn as much as possible so one can reach the level that he/she is really serving our master in the way we should. Needless to say how much Tefila effects our soul and connection to G-od, therefore I would recommend to learn about Tefila as much as possible Rabbi Alon Anava