The week begins on Sunday. The working week typically begins on Monday, which is different.
That is incorrect, if you are from pagan, celt, or druid descent that is, which most (just.............still....just) English persons are - not withstanding viking invasion, Rome occupation and............well you get the point I'm sure.
The 'Sunday' was traditionally used as the final day within a period of 7, where the sun was worshipped and given thanks by peoples for the warmth it gave, the light it produced, the security it provided during what was termed as the 'day' and finally the growth it offered to trees, plants and crops.
The 'Sunday' therefore, was the final day of a circle of '7'. The working week, Monday etc and all of that argument doesn't even come into it.
Personally, I much prefer 'Intraweek Transitionary Period'.
;-)