Anglo-Saxon Week

In Heathen times, time was judged very differently from what we are used to today, our knowledge of their system of judging time is sadly lacking, but enough information has survived to give us a rough idea
how it worked. At some stage the Germanic peoples accepted the Roman calendar and seven day week. The Romans named their days after some of their gods and goddesses, but when the Germanic peoples accepted the Roman week, they didn't accept their names, with the exception of Saturn for Saturday. Instead it seems that they replaced the Roman god names for those of their native gods and goddesses that were closest in image and character to the Roman ones.
For example the Roman war god Mars was replaced by the Germanic war god Tiw/Tyr and so on.


Roman Name: Old English: Modern English:
dies Lunae : Monnandaeg : Monday
dies Martis : Tiwesdaeg : Tuesday
dies Mercuri : Wodnesdaeg : Wednesday
dies Jovis : Thunresdaeg : Thursday
dies Veneris : Frigedaeg : Friday
dies Saturni : Sæterdaeg : Saturday
dies Solis : Sunnandaeg : Sunday


The day was also very different too, whereas today for example Monday starts at midnight and finishes the following midnight, which then becomes Tuesday, the days back then were judged to start and finish at sunset and sunrise. At sunset for example Monnandaeg or Monday became Tiwesniht, which means Tiw's eve, and then at sunrise Tiw's eve became Tiwesdaeg or Tuesday, which again at sunset became Wodnesniht or Woden's eve and so on.

After Sunrise

Sunnandaeg (Sun's day)
Monnandaeg (Moon's day)
Tiwesdaeg (Tiw's day)
Wodnesdaeg (Woden's day)
Thunresdaeg (Thunor's day)
Frigesdaeg (Frige's day)
Sæterdaeg (Saturn's day)

After Sunset

Monnanniht (Moon's eve)
Tiwesniht (Tiw's eve)
Wodnesniht (Woden's eve)
Thunresniht (Thunor's eve)
Frigeniht (Frige's eve)
Sæterniht (Saturn's eve)
Sunnaniht (Sun's eve)

Days themselves seem to have been counted in nights, which can be seen in the word fortnight, which means fourteen nights, roughly half the length of a lunar month. For people today the 'old week' system may seem strange, but for the Heathens it worked well, and much of it, especially the names are still with us today.

http://www.homestead.com/englishheathenism/anglosaxonweek.html