Javascript Date adjust(yr,mn,dy,hr,mi,se)

Date.prototype.adjust = function(yr,mn,dy,hr,mi,se) {
 var m,t;// w  w w .  j a v  a2s .  c o m
 this.setYear(this.getFullYear() + yr);
 m = this.getMonth() + mn;
 if(m !== 0) { this.setYear(this.getFullYear() + Math.floor(m/12)); }
 if(m < 0) {
  this.setMonth(12 + (m%12)); 
 } else if(m > 0) {
  this.setMonth(m%12);
 }
 t = this.getTime();
 t += (dy * 86400000);
 t += (hr * 3600000);
 t += (mi * 60000);
 t += (se * 1000);
 this.setTime(t);
}