In Arabic dates off the week are numbered 1-7. In English and other similar languages, they are named after 'gods' and 'goddesses'.
But hoe it's or that the Friday of one week matches the equivalent of the Islamic week? Why are they not misaligned liked the months (albeit with a fixed offset)?
This is answered elsewhere, in this history.stackexchange answer (excerpt):
In the ancient world there were two forms of the seven-day week. First, the Jewish week (eventually adopted by Christians and Muslims) has numbered days from one (Sunday) to six (Friday) and the Sabbath on the seventh day.
Because the days of the week don't necessarily have to tie up with the days of the year (e.g. Jan 1 is not always a Friday), the days of the week they've stayed in step throughout the ages.
