American Independence Day is on 4 July, commemorating the country’s declaration of independence from Britain in 1776. In the novel, the USA no longer exists and the celebration is therefore redundant.
Labor Day is a federal American holiday on the first Monday in September. It was first organised by Peter J. McGuire, an American labour leader, after he had witnessed Canadian labour disputes which led to a law protecting unionism in Canada. The first American Labour Day parade took place in New York City in 1882, as a celebration of the workers and their families. Today, the celebration still includes parades and political speeches.