I got one weird issue with Date object initialization. And wondering if someone can explain why..
var exp1 = new Date('2014-10-17');
var exp2 = new Date(2014,9,17);
var exp3 = new Date('17 Oct 2014');
console.log(exp1);
console.log(exp2);
console.log(exp3);
Results:
Thu Oct 16 2014 18:00:00 GMT-0600 (MDT) // 16th?
Fri Oct 17 2014 00:00:00 GMT-0700 (MST) // Why GMT -7
Fri Oct 17 2014 00:00:00 GMT-0600 (MDT) // The only one that works as expected
Why are these three Date objects so different?
The first date is treated as GMT since no time zone offset is provided. When logged out it shows the time in your local timezone. Adding an offset (exp4 below), I get the date expected.
var exp1 = new Date('2014-10-17');
var exp2 = new Date(2014,9,17);
var exp3 = new Date('17 Oct 2014');
var exp4 = new Date('2014-10-17z-0500');
Results:
Thu Oct 16 2014 19:00:00 GMT-0500 (Central Daylight Time)
Fri Oct 17 2014 00:00:00 GMT-0500 (Central Daylight Time)
Fri Oct 17 2014 00:00:00 GMT-0500 (Central Daylight Time)
Fri Oct 17 2014 00:00:00 GMT-0500 (Central Daylight Time)
I am not sure about exp2 for you, but suspect it has something to do with daylight savings time and that you live in an area that does not observe daylight savings (Arizona?).
Edit: this seems to be browser specific. The results above were generated in Chrome while in IE 11, exp4 was an invalid date. For IE 11 I had to use this format:
var exp4 = new Date('2014-10-17T00:00-05:00');
Related
The code:
console.log(start)
reads, Thu Mar 01 2018 00:00:00 GMT+0530 (India Standard Time)
I want it a new object start_NY which will read Thu Mar 01 2018 00:00:00 w.r.t. America/New_York timezone. Something like Thu Mar 01 2018 00:00:00 GMT-0500.
I used a script:
start_ny = new Date('Thu Mar 01 2018 00:00:00 GMT-0500');
But that reads, Thu Mar 01 2018 10:30:00 GMT+0530 (India Standard Time), which is actually converting the date into Indian Standard Time, instead of giving me a time from New_York timezone.
The format should be same as that of the existing one. How can I do that?
Try with this following code and MDN resources
new Date().toLocaleString('en-US', { timeZone: 'America/New_York' })
// Date Format
new Date().toDateString('en-US', { timeZone: 'America/New_York' });
I get inconsistent timezone based on params to Date():
new Date()
Sun Oct 25 2015 18:10:42 GMT+0200 (IST)
new Date(1445720400)
Sat Jan 17 1970 19:35:20 GMT+0200 (IST)
new Date(144572040000)
Thu Aug 01 1974 09:54:00 GMT+0300 (IDT)
new Date(14457204000000)
Thu Feb 17 2428 20:00:00 GMT+0200 (IST)
I tried reading the docs or finding an explanation to this weirdness, but couldn't.
I've checked on both Chrome 46 and Safari 7.1.8,
Any ideas?
Isn't this just daylight savings? One of the dates happened to be in the summer?
The problem in then you set different time in ms as param for 'new Date()'. And you have different time zones because the Date has been generated in different seasons (Summer's time and Winter's time). It is normal.
> new Date('2015-1-1')
Thu Jan 01 2015 00:00:00 GMT-0500 (EST)
> new Date('2015-01-1')
Thu Jan 01 2015 00:00:00 GMT-0500 (EST)
> new Date('2015-1-01')
Thu Jan 01 2015 00:00:00 GMT-0500 (EST)
// Yet...
> new Date('2015-01-01')
Wed Dec 31 2014 19:00:00 GMT-0500 (EST)
// Similarly:
> new Date('2015-1-10')
Sat Jan 10 2015 00:00:00 GMT-0500 (EST)
> new Date('2015-01-10')
Fri Jan 09 2015 19:00:00 GMT-0500 (EST)
Can't figure out why this is happening (Chrome 39). Is it related to octal parsing?
Firefox only accepts new Date('2015-01-10'), and returns what I expect: Date 2015-01-10T00:00:00.000Z
Found the answer in a related question; it appears Chrome parses the YYYY-MM-DD format as UTC time, then converts it the local timezone. So, 2015-01-01 00:00:00 in UTC is Dec 31 in EST.
See Inconsistencies when creating new date objects:
It looks like the form '1979-04-05' is interpreted as a UTC date (and then that UTC date is converted to local time when displayed).
Apparently, a possible cross browser solution is to replace the dashes with slashes to force using local time:
new Date('2015-01-10'.replace(/-/g, '/'))
I am unsure of your problem since My chrome(39.0.2171.99) gives me Jan 01 in all case. But having said this, I would like to point out that you should probably use
new Date(2015,1,1)
This is how JS Date is supposed to be initialised.
I have just noticed some strange behavior in one of my Arrays. I am sure the issue is with how Javascript stores object references in arrays. I will demonstrate the issue with a bit of code I posted as an answer to another question on SO. The code, just loops to get todays date and the 6 previous dates of the month, pretty self explanatory.
var dates = [];
var date = new Date();
for (var i = 0; i < 7; i++){
var tempDate = new Date();
tempDate.setDate(date.getDate()-i);
dates.push(tempDate);
}
console.log(dates);
Output: [Thu Jun 05 2014 14:54:14 GMT+0100 (GMT Daylight Time),
Wed Jun 04 2014 14:54:14 GMT+0100 (GMT Daylight Time),
Tue Jun 03 2014 14:54:14 GMT+0100 (GMT Daylight Time),
Mon Jun 02 2014 14:54:14 GMT+0100 (GMT Daylight Time),
Sun Jun 01 2014 14:54:14 GMT+0100 (GMT Daylight Time),
Sat May 31 2014 14:54:14 GMT+0100 (GMT Daylight Time),
Fri May 30 2014 14:54:14 GMT+0100 (GMT Daylight Time)]
This is correct, and is expected, as tempDate is continually recreated as a new Date object inside of the loop.
When I take tempDate out of the loop however, it seems to update all of the objects in the array every iteration of the loop (also the loop seems to go one Month and 1 day too far to 29th apr):
var dates = [];
var date = new Date();
var tempDate = new Date();
for (var i = 0; i < 7; i++){
tempDate.setDate(date.getDate()-i);
dates.push(tempDate);
}
console.log(dates);
Output: [Tue Apr 29 2014 14:52:21 GMT+0100 (GMT Daylight Time),
Tue Apr 29 2014 14:52:21 GMT+0100 (GMT Daylight Time),
Tue Apr 29 2014 14:52:21 GMT+0100 (GMT Daylight Time),
Tue Apr 29 2014 14:52:21 GMT+0100 (GMT Daylight Time),
Tue Apr 29 2014 14:52:21 GMT+0100 (GMT Daylight Time),
Tue Apr 29 2014 14:52:21 GMT+0100 (GMT Daylight Time),
Tue Apr 29 2014 14:52:21 GMT+0100 (GMT Daylight Time)]
So the two questions I pose are:
Why does the object stored in the array keep mutating with every
iteration? (I suspect this is because of the way Javascript is
storing the references to the object, but an explanation would be
nice)
Why does the loop run one too far in the second bit of code? The first example shows the loop ends after 7 successful iterations, on May the 30th (7 days in the past), the second example shows the resultant date after the iterations as the 29th april - more than a month into the past. Why?
edit: I have a rudimentary jsfiddle, to allow testing the code.
var tempDate = new Date(); creates new object. so in this example:
var array = [tempDate,tempDate,tempDate,tempDate,tempDate];
array[0] is same object as array[1]
this is just how objects works in almost every programming language:
var a = tempDate;
var b = tempDate;
var c = b;
(in above example a, b, c, and tempDate is same thing)
Regarding question 2:
please have a look at this fiddle http://jsfiddle.net/Mqnmm/
with new object tempDate is always today, then you apply setDate()
with old object, before last literation date is Sat, 31 May 2014 14:23:34 GMT, then you apply tempDate.setDate(-1) which sets date to last N days of previous month
Subtract days from a date in JavaScript please check Rob Dawley`s answer to properly adjust dates
When I construct a date object from a string, I am getting confusing results. It seems as if the time is chosen arbitrarily (but repeatably) if I don't specify it.
var d1=new Date("2013-10-9"), d2=new Date("2013-10-10");
output = d1+' '+d1.toUTCString()+'<br>\n';
output += d2+' '+d2.toUTCString()+'<br>\n';
Chromium 20.0...
Wed Oct 09 2013 00:00:00 GMT-0600 (MDT) Wed, 09 Oct 2013 06:00:00 GMT
Wed Oct 09 2013 18:00:00 GMT-0600 (MDT) Thu, 10 Oct 2013 00:00:00 GMT
Why would Chromium choose a different time on October 10?
By the way, the workaround is here: https://stackoverflow.com/a/744134/86967
It has to do with the format of the date string you are using. If you specify 2013-10-09 (notice the extra 0 on the day), then it works as expected. If you use 2 digits for the day and month, then you are following the ECMA spec.
var d1=new Date("2013-10-09"), d2=new Date("2013-10-10");
console.log(d1+' '+d1.toUTCString());
console.log(d2+' '+d2.toUTCString());
Yields:
Tue Oct 08 2013 20:00:00 GMT-0400 (Eastern Daylight Time) Wed, 09 Oct 2013 00:00:00 GMT
Wed Oct 09 2013 20:00:00 GMT-0400 (Eastern Daylight Time) Thu, 10 Oct 2013 00:00:00 GMT
I believe the code they are using can be found here:
https://github.com/WebKit/webkit/blob/master/Source/WTF/wtf/DateMath.cpp
When you provide an ECMA date, it will use the parseES5DateFromNullTerminatedCharacters method to parse the date, but when you use a non-standard date format it will use the parseDateFromNullTerminatedCharacters method. I am not that familiar with the webkit code, so I could be wrong, but this is based on my reading of the parsing logic.
The standard date format can be found in section 15.9.1.15 of the ECMA Spec.