today = new Date();
var curr = new Date; // get current date var first = curr.getDate() - curr.getDay(); // First day is the day of the month - the day of the week var last = first + 6; // last day is the first day + 6 var firstday = new Date(curr.setDate(first)).toUTCString(); var lastday = new Date(curr.setDate(last)).toUTCString(); firstday "Sun, 06 Mar 2011 12:25:40 GMT" lastday "Sat, 12 Mar 2011 12:25:40 GMT"
This works for firstday = sunday of this week and last day = saturday for this week. Extending it to run Monday to sunday is trivial.
Making it work with first and last days in different months is left as an exercise for the user