There is a saying: "The fourth day is for receiving the gods and the fifth day separates the holidays from the rest of the year." When the gods return, this period of laying aside one's duties is at an end. Many businesses also pick a time on the fifth to set off firecrackers and worship the gods, officially reopening and getting back to work!
所謂「初四接神，初五隔開」，一旦天神回返人間，代表過年放鬆無序的狀態告一段落，商家也在初五這一天擇定吉時，鳴砲祭神，開張大吉，迎接新的一年，重新打拚！