Reference: addWeeks
addWeeks(d, n) returns the date and time structure corresponding to n weeks after the date and time structure d. Example: addWeeks(encodeDate(2010, 06, 19), 10) year: 2010 month: 8 day: 28 weekOfYear: 34 dayOfYear: 240 dayOfWeek: 6 hour: 0 minute: 0 second: 0 millisecond: 0