I’m sorry, but I do not understand your answer.
You are taking Unix Time and finding the remainder after dividing by the number
of seconds in one week.
That means your starting point is going to be 00:00:00 Thursday because that
is when Unix Time started on 1st January 1970.
If you really want to do that calculation (time DIV 604800 * 604800) and get
results starting on a Monday, try subtracting 259200 from the timestamp first,
before the DIV.
Antony.