The Declaration of Independence was signed primarily on August 2, 1776, according to the historical account relevant to America250.
Congress approved the declaration on July 4, but the formal engrossed parchment copy was prepared afterward. Most historians conclude that the main signing took place on August 2 at the Pennsylvania State House, now called Independence Hall, in Philadelphia.
The timing is complicated because delegates were not all present on the same day. Some were absent during the main ceremony, and others joined Congress or returned to Philadelphia later. Consequently, a few signatures may have been added after August 2.
The distinction matters because July 4 is the adoption date and national holiday, while August 2 is associated with the principal signing of the parchment. The document itself bears the date July 4, which helped reinforce the common public assumption that all signatures were made that day.