Question: On what two days does federal law require American flags to be flown at half staff? Answer: Memorial Day (last Monday in May) and May 15, National Peace Officers Memorial Day.

This tribute to American law enforcement officers is part of the historic crime bill that President Bill Clinton signed into law in 1994. At the request of the National Law Enforcement Officers Memorial Fund, Public Law 103-322 designates Peace Officers Memorial Day as one of only two days each year during which government agencies, businesses and residents are to fly their U.S. flags at half-staff.

"We honor our law enforcement officers every day of the year, but on Peace Officers Memorial Day, we show our support by lowering our flags to half-staff,” said Craig W. Floyd, Memorial Fund Chief Executive Officer. “Our officers deserve the respect of the communities and country they keep safe. And we will do our part by lowering the flags at the Memorial, where the names of more than 21,000 fallen officers are engraved."

In 1962, President Kennedy proclaimed May 15 as National Peace Officers Memorial Day and the calendar week in which May 15 falls, as National Police Week. Established by a joint resolution of Congress in 1962 , National Police Week pays special recognition to those law enforcement officers who have lost their lives in the line of duty for the safety and protection of others.

As part of National Police Week, the names of 129 law enforcement officers killed in 2017, as well as 231 officers who died in prior years , will be formally dedicated on the National Law Enforcement Officers Memorial in Washington, DC, on May 13, during the 30th Annual Candlelight Vigil.