One Day in History was a single-day initiative by several UK heritage organisations that aimed to provide a historical record of the everyday life of the British public in the early 21st century. Described as the "world's biggest blog", it encouraged UK citizens to write diary entries of 100–650 words of what they had done on 17 October 2006, and then upload them to the official website of the initiative. The project formed a part of , a history campaign led by several UK heritage organisations