a simple javascript library to get day or timestamp

Date.prototype.getTimestamp = function(format){//the separatings line can be "-" ,'/' or '.' or else
var currentTime = new Date();
var thisYear = currentTime.getFullYear();
var thisMonth = currentTime.getMonth()+1;
var today = currentTime.getDate();
var hh = currentTime.getHours();
var mm = currentTime.getMinutes()>10?currentTime.getMinutes():("0"+currentTime.getMinutes())
var ss = currentTime.getSeconds()>10?currentTime.getSeconds():("0"+currentTime.getSeconds());
return ( format.replace(/(y{2,4})/,thisYear).replace('MM',thisMonth).replace('dd',today).replace('hh',hh).replace('mm',mm).replace('ss',ss));

}

Date.prototype.getSomeDay = function(someday){
var weekend=['Sun','Mon','Tue','Wed','Thu','Fri','Sat'];
var now = someday.split(/[\-|\/|\.]/);
var thisYear = parseInt(now[0]);
var thisMonth = parseInt(now[1].replace(/(^0)/,''));
var today = parseInt(now[2].replace(/(^0)/,''));
if(thisMonth == 1) {
thisMonth = 13;
thisYear-=1;
}
if(thisMonth ==2){
thisMonth =14;
thisYear-=1;
}
var week=Math.round((today+2*thisMonth+3*(thisMonth+1)/5+thisYear+thisYear/4-thisYear/100+thisYear/400)%7);
return weekend[week];
}