Taps ("Butterfield's Lullaby"), sometimes known by the lyrics of its second verse, "Day is Done," is a famous musical piece, played in the U.S. military during flag ceremonies and funerals, generally on bugle or trumpet. The tune is also used at night to signal "lights out".

The bugle call was composed by the Union Army Brigadier General Daniel Butterfield, an American Civil War general who commanded the 3rd Brigade of the 1st Division in the V Army Corps of the Army of the Potomac. Butterfield wrote the tune at Harrison's Landing, Virginia, in July 1862. Taps also replaced "Tattoo", the French bugle call to signal "lights out". Butterfield's bugler, Oliver W. Norton, of Chicago, was the first to sound the new call. Within months, Taps was used by both Union and Confederate forces. Villanueva (see external link "Detailed History of Taps" below) states that the tune is actually a variation of an earlier bugle call known as the Scott Tattoo which was used in the U.S. from 1835 until 1860.

A bugler plays Taps during the funeral of Caspar W. Weinberger in Arlington National CemeteryTaps concludes nearly 15 military funerals conducted with honors each weekday at Arlington National Cemetery, as well as hundreds of others around the United States.[citation needed] The tune is also played at many memorial services in Arlington's Memorial Amphitheater and at gravesites throughout the cemetery.

Taps is sounded during each of the 2,500 military wreath ceremonies conducted at the Tomb of the Unknowns every year, including the ones held on Memorial Day. The ceremonies are viewed by many people, including veterans, school groups, and foreign officials. Taps is also played nightly at 10 PM (2200 hrs) in military installations at non-deployed locations to indicate that it is "lights out". When Taps is played, it is customary to salute if in uniform, or to place the right hand over the heart if out of uniform. While there are no official lyrics, and the original version was purely instrumental, there have been several later lyrics added. The most common form is shown below: