The Happy Monday System (ハッピーマンデー制度, Happī Mandē Seido) is a set of modifications to Japanese law in 1998^[1] and 2001^[2] to move a number of public holidays in Japan to Mondays, creating three-day weekends for those with five-day work weeks. It is the Japanese equivalent of the 1968 Uniform Monday Holiday Act in the United States.

• Public holidays in Japan
• Japanese calendar
• Japanese festivals
• Uniform Monday Holiday Act (similar legislation in the United States)