// Get the "coordinates" for the date relative to the month currently displayed.
// using (day, week): upper left coord is (1, 1), lower right coord is (7, 6)
// if the date isn't visible (-1, -1) is put in (day, week) and false is returned
// Get the "coordinates" for the date relative to the month currently displayed.
// using (day, week): upper left coord is (1, 1), lower right coord is (7, 6)
// if the date isn't visible (-1, -1) is put in (day, week) and false is returned