Field Day is held annually on the fourth full weekend in June.
Full details and rules about ARRL Field Day can be found on the ARRL web site.
From the ARRL Website-- Objective :To work as many stations as possible on any and all amateur bands (excluding the 60, 30, 17, and 12-meter bands) and to learn to operate in abnormal situations in less than optimal conditions. Field Day is open to all amateurs in the areas covered by the ARRL/RAC Field Organizations and countries within IARU Region 2. DX stations residing in other regions may be contacted for credit, but are not eligible to submit entries.