Astronomy Day was started in 1973 by Doug Berger, the president of the Astronomical Association of Northern California. The purpose is to provide interaction between the general public and various astronomy enthusiasts, groups, and professionals. The date of Astronomy Day changes every year. It always occurs between mid-April and mid-May, on the Saturday before or on the first quarter moon. Next year, Astronomy Day will be observed on May 10th.

Astronomy Week is scheduled around Astronomy Day. Astronomy Week begins the Monday before and ends on the Sunday after Astronomy Day. This year, Astronomy Week begins on Monday, April 16th and ends on Sunday, April 22nd. Next year, Astronomy Week will be May 5th through May 11th.