setUTCMonth()

var myDate = new Date()
// assume myDate = Wed Aug 1 2001
var currDate = myDate.setUTCMonth(4)
var showDate = myDate
// showDate = Mon Apr 9 2001
var currDate = myDate.setUTCDate(-13)
showDate = myDate
// showDate = Sun Jan 9 2000

Note:

The day of the week is automatically worked out by the system.