Ancient Jewish tradition placed Sunday as the first day, with Saturday being the day of rest in honor of God's post-creation rest. Europe inherited this numbering via Christianity, which moved the day of rest to Sunday, still the first day, in honor of Jesus' resurrection. The church sometimes also refers to Sunday figuratively as the eighth day, in anticipation of being outside of time in heaven. Europeans 1000 years ago had a workweek from Monday through Saturday, and had Sunday off if they were lucky, plus several assorted special days off throughout the year. The past century gave many of us a shorter workweek, and in parts of Europe a new first day of the week, Monday. In Europe the seven days of the week were originally named, in Greek or Germanic, after the seven planets visible to ancient and medieval astronomers, in order by day: Sun (1=Sunday=Sonntag), Moon (...), Mars, Mercury, Jupiter, Venus, Saturn. In German the "Wodan~Mercury" connection with the fourth day was replaced by the positional "mid-week" term "Mittwoch". I find it an interesting paradox that, as in the case above, sometimes in German a germanic root is lost, whereas in a derived language like English it is retained. Another example is English "window" (a germanic "wind-eye" or "Wind-Auge") versus German "Fenster" (ultimately from Latin).