Language & WorldFact
In Portuguese, Monday is called "second day".
Almost every European language names weekdays after planets and gods: mardi after Mars, Thursday after Thor. Not Portuguese: segunda-feira, terça-feira, quarta-feira count the second to sixth day; only sábado and domingo remain. The reason is Martin of Braga, a 6th-century bishop who wanted no pagan gods in the calendar. Only Portuguese and Mirandese kept it up.
Useful: If Portuguese confuses you: "quinta" is Thursday because Sunday counts as day one.
Source: en.wikipedia.org