The National Day of Prayer (36 U.S.C. § 119) is an annual day of observance held on the first Thursday of May, designated by the United States Congress, when people are asked "to turn to God in prayer and meditation". Each year since its inception, the president has signed a proclamation, encouraging all Americans to pray on this day.
The modern law formalizing its annual observance was enacted in 1952, although earlier days of fasting and prayer had been established by the Second Continental Congress from 1775 until 1783, and by President John Adams in 1798 and 1799. Most presidents have issued annual or special occasion proclamations for a national day of prayer, with the notable exception of Andrew Jackson. Thomas Jefferson also issued a day of prayer and thanksgiving, but this occurred while serving as governor of Virginia.
The constitutionality of the National Day of Prayer was unsuccessfully challenged in court by the Freedom From Religion Foundation after their first attempt was unanimously dismissed by a federal appellate court in April 2011.