WEEKS("2002-19-02 ";" 2002-19-02 "; 1) returns 0, because there is not a whole week in between, starting at the first day of the week (monday or sunday, depending on your local settings)
WIKEN ("2007- 19- 02"; "2007- 19- 02"; 1) jout 0, omdat der gjin hiele wike tusken dizze data sit, besjoen sûnt de earste dei fan de wike( ôfhinklik fan jo lokale ynstellingen is dat snein of moandei)