For America - (although all are free to join in)
The history of the National Day of Prayer
and from those at WikiWacki -> 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. <===linky dinky you clicky to see it all
It's today !....