Date.UTC() returns last day of previous month while getUTCFullYear(), getUTCMonth() returns correctly first day of correct month

Question

I'm getting a strange result:

   var date = new Date();
   var year  = date.getMonth() < 11 ? date.getFullYear() : date.getFullYear() + 1;
   var month = date.getMonth() < 11 ? date.getMonth() + 1 : 0;

   console.log(new Date(Date.UTC(year, month)));

   var utcYear = date.getUTCMonth() < 11 ? date.getUTCFullYear() : date.getUTCFullYear() + 1;
   var utcMonth = date.getUTCMonth() < 11 ? date.getUTCMonth() + 1 : 0;

   console.log(new Date(utcYear, utcMonth));

With the particular date I'm using (any date will do), Date.UTC gives me:

Sun May 31 2015 19:00:00 GMT-0500 (Central Daylight Time)

The getUTC... aproach gives me:

Mon Jun 01 2015 00:00:00 GMT-0500 (Central Daylight Time)

Am I mis-using Date.UTC or am I missing something?

Thanks

Answer 1

You are creating a Date using UTC time, but then you are displaying it in local time, that's why it's a few hours behind. Use Date.prototype.toUTCString() to see the UTC time

  var date = new Date();
  var year = date.getMonth() < 11 ? date.getFullYear() : date.getFullYear() + 1;
  var month = date.getMonth() < 11 ? date.getMonth() + 1 : 0;

  // It's a UTC date, display it as UTC, not local time
  console.log(new Date(Date.UTC(year, month)).toUTCString());

  var utcYear = date.getUTCMonth() < 11 ? date.getUTCFullYear() : date.getUTCFullYear() + 1;
  var utcMonth = date.getUTCMonth() < 11 ? date.getUTCMonth() + 1 : 0;

  // Created using local time, you can just use the normal toString()
  console.log(new Date(utcYear, utcMonth));