If there is 31-days in Janurary, and the first day begin on Thursday. How do I determine four weeks and seven days. Do I count the first three days as week one. Followed with the remaining three weeks.

Answer 1

Four weeks and seven days (=5 weeks) from January first which is a Thursday (see calendar of 2009)
Su Mo Tu We Th Fr Sa
0 0 0 0 1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31

The first line may be shifted, sorry.

So four weeks finish on the 28th, add three days to finish January, and another four days in February will do the job.