For America250, the United States Declaration of Independence is dated to its adoption on July 4, 1776.
The Second Continental Congress adopted the document in Philadelphia after debating a resolution for independence. The Declaration announced that the Thirteen Colonies considered themselves free and independent states rather than subjects of the British Crown.
July 2 is sometimes mentioned because Congress passed the Lee Resolution declaring independence on that date. The Declaration itself, however, was adopted on July 4, the date that became the basis for Independence Day and the America250 anniversary.
The famous parchment copy bears the date July 4, although most delegates are believed to have signed it primarily on August 2. Adoption, public issuance, and later signing are related events but are not identical.