Determination of the day of the week possible to do all the calculations in one's head with a little practice). None of the methods given here perform range checks, so unreasonable dates will produce erroneous results. Every seventh day in a month has the same name as the previous: "Corresponding months" are those months within the calendar year that start on the same day of the week. For example, September and December correspond, because September 1 falls on the same day as December 1. Months can only correspond if the number of days between their first days is divisible by 7, or in other words, if their
Labor Day such a public celebration, owing to optimum weather and the date's place on the calendar, sitting midway between the Fourth of July and Thanksgiving public holidays. Labor Day picnics and other public gatherings frequently featured speeches by prominent labor leaders. In 1909 the American Federation of Labor convention designated the Sunday preceding Labor Day as "Labor Sunday", to be dedicated to the spiritual and educational aspects of the labor movement. This secondary date failed to gain significant traction in popular culture. In 1887 Oregon became the first state of the United States to make Labor Day an official public holiday.