TimeZoneOffset Problems

I have a current time (EST) function in my website thats supposed to show the time in Washington DC. I thought that the timezone offset is -4 so i wrote this code;

dt = new Date();
UTC = trace(dt.getUTCHours()+(-4) + “:” + dt.getUTCMinutes());
myTime = dt.getUTCHours()+(-4) + “:” + dt.getUTCMinutes()

However after 8:00PM the time starts to act up and shows incorrectly, for example when it is 8:00PM the time shows “-4:0”, when it is 10:00 it shows “-2:0” , also not showing the second digit for the minutes. Please help.