Saturday is Saturn's day and corresponds to the Saturn Period.
Sunday is the Sun's day and corresponds to the Sun Period.
Monday is the Moon's day and corresponds to the Moon Period.
Tuesday is the day of the Norse war-god, Tyr, and corresponds to the
Mars-half of the Earth Period.
Wednesday is the day of the Norse Mercury, Wotan, and corresponds to
the Mercury-half of the Earth Period.
Thursday is the day of Thor, the Norse Jupiter, and corresponds to the
Jupiter Period.
Friday is the day of the Norse Venus, Freia, and corresponds to the
Venus Period.