Local bars have the option of staying open one hour later tonight because tomorrow is a D.C. holiday.

D.C. Emancipation Day celebrates how slaves in D.C. were freed months before President Abraham Lincoln’s Emancipation Proclamation. On April 16, 1862 Lincoln signed the Compensated Emancipation Act, which made slaves in D.C. the first in the country to be freed by the federal government. This day was made an official public holiday in 2005.

DCist has the details on why bars in the District can stay open later. A law was passed last year making it possible for the additional hour of service the night before a D.C. or federal holiday.