I remember when I was fourteen years old going to a lock-in in Dothan, Alabama with my mother and stepfather. While playing a lot of sports and dancing, I also remember the sermon that was given during Sabbath services, although I have forgotten the name of the person who gave the message. The topic of the messages was on the names of the days of the week. Having never thought about the subject before, I was struck by the connection that the speaker made between the heathen days of the week and the biblical passages like Psalm 16:4, which reads: “Their sorrows shall be multiplied who hasten after another god; Their drink offerings of blood I will not offer, Nor take up their names on my lips,” which speak negatively about the mentioning of the names of other gods, and after that in my own personal journal after that I marked the days of the week as day one, day two, day three, day four, day five, day six, and Sabbath, respectively.
Why do I bring this up, seeing as this is an obscure sort of personal habit that would be of interest to few people? It so happens that in Portuguese history there was a minister like the one I heard that managed to convince the entire nation of Portugal that it was wrong to have days of the week that were connected to heathen deities and as a result the Portuguese language itself refers to its days as domingo segunda-feira, terça-feira, quarta-feira, quinta-feira, sexta-feira, and sábado. With the exception of the first day of the week, which could easily just be called primera-feira because the Sabbath is the Lord’s Day , this is a very sensible way to name days, and it preserves the knowledge that the Sabbath is the seventh day of the week, something that is occasionally forgotten by makers of calendars which view the first day of the work week as the first day of the week.
This particular story is a demonstration of the fact that one can be right for the wrong reasons. It is thought–though documentation is difficult to come by, that this change is due to the religious preaching of a sixth century bishop of Braga named Martinho de Dume, who wanted the days of the week to be named after the supposed “holy week” before Easter, itself with a name that springs from Middle Eastern heathen religious thought. And, quite notably, the bishop was apparently successful in encouraging the Portuguese faithful to rename their days of the week so as to be numerical in nature rather than pointing to heathen purposes. It should also be noted that this avoidance of heathen names does not hold true in the Portuguese naming of the months, which like those in English have extensive references to heathen Roman deities like Janus (January), Mars (March), Maia, a Roman earth goddess (May), and Juno, wife of Jupiter (June). That is to say nothing about the folly of naming months after Julius and Augustus Caesar, who were worshiped as gods by the heathen state worship of the Roman Empire. At least the 9th-12th months have ordinal names, even if they end up being for 7th-10th instead of the order of the months they currently have in our calendar, but it’s at least a good start.
 See, for example: