UTC Times in JavaScript

I am trying to get the current UTC date to store in my database. My local time is 9:11 pm This equates to 1:11 am UTC. When I look in my database, I notice that 1:11 pm is getting written to. I'm confused. In order to get the UTC time in JavaScript, I'm using the following code:

var currentDate = new Date();
var utcDate = Date.UTC(currentDate.getFullYear(), currentDate.getMonth(), currentDate.getDate(), currentDate.getHours(), currentDate.getMinutes(), currentDate.getSeconds(), currentDate.getMilliseconds());
var result = new Date(utcDate);

What am I doing wrong?

---

A lttle searching turned out you can do this:

var now = new Date(),
    utcDate = new Date(
        now.getUTCFullYear(),
        now.getUTCMonth(),
        now.getUTCDate(),
        now.getUTCHours(),
        now.getUTCMinutes(), 
        now.getUTCSeconds()
    );

Even shorter:

var utcDate = new Date(new Date().toUTCString().substr(0, 25));

How do you convert a JavaScript date to UTC?

It is a commonly used way, instead of creating a ISO8601 string, to get date and time of UTC out. Because if you use a string, then you'll not be able to use every single native methods of Date() , and some people might use regex for that, which is slower than native ways.

But if you are storing it in some kind of database like localstorage , a ISO8601 string is recommended because it can also save timezone offsets, but in your case every date is turned into UTC, so timezone really does not matter.

---

If you want the UTC time of a local date object, use the UTC methods to get it. All javascript date objects are local dates.

var date = new Date(); // date object in local timezone

If you want the UTC time, you can try the implementation dependent toUTCString method:

var UTCstring = date.toUTCString();

but I wouldn't trust that. If you want an ISO8601 string (which most databases want) in UTC time then:

var isoDate = date.getUTCFullYear() + '-' +
              addZ((date.getUTCMonth()) + 1) + '-' +
              addZ(date.getUTCDate()) + 'T' +
              addZ(date.getUTCHours()) + ':' +
              addZ(date.getUTCMinutes()) + ':' +
              addZ(date.getUTCSeconds()) + 'Z';

where the addZ function is:

function addZ(n) {
  return (n<10? '0' : '') + n;
}

Modify to suit.

Edit

To adjust a local date object to display the same time as UTC, just add the timezone offset:

function adjustToUTC(d) {
  d.setMinutes(d.getMinutes() + d.getTimezoneOffset()); 
  return d;
}

alert(adjustToUTC(new Date())); // shows UTC time but will display local offset

Take care with the above. If you are say UTC+5hrs, then it will return a date object 5 hours earlier but still show "UTC+5"

A function to convert a UTC ISO8601 string to a local date object:

function fromUTCISOString(s) {
  var b = s.split(/[-T:.Z]/i);
  var n= new Date(Date.UTC(b[0],b[1]-1,b[2],b[3],b[4],b[5]));
  return n;
}

alert(fromUTCISOString('2012-05-21T14:32:12Z'));  // local time displayed

链接地址: http://www.djcxy.com/p/59578.html

上一篇: SQL Azure兼容级别

下一篇: UTC时间在JavaScript中