To set the month value using local time, use the setMonth method.
If the value of numMonth is greater than 11 (January is month 0), or is a negative number, the stored year is incremented or decremented appropriately. For example, if the stored date is "Jan 5, 1996 00:00:00.00", and setUTCMonth(14) is called, the date is changed to "Mar 5, 1997 00:00:00.00."
The setUTCFullYear method can be used to set the year, month, and day of the month.
var d, s; // Declare variables.
d = new Date(); // Create Date object.
d.setUTCMonth(newmonth); // Set UTC month.
s = "Current setting is ";
s += d.toUTCString();
return(s); // Return new setting.