Lord Caitanya's Birthdate is on the Phalguna Purnima between 15 of Feb. and 15th of March. The full moon day is Lord Caitanya's Birthday. I think you can send for Rayarama's calendar which he has published. The exact day is 14th March, Thursday, 1968. The procedure is that you should fast from morning to evening (about 7:00) after that there should be offering to Lord Caitanya and prasadam should be accepted just like on Ekadasi day, and next day, Friday, full love feasting may be provided to as many devotees as you can.
Srila Prabhupada's Letter to: Janardana — Los Angeles 21 January, 1968