We Keep Coding

Why the toISOString() applied on a Date object generate a wrong time section converting a date into a string?

I am going crazy with this Date to String conversion into a TypeScript project:
I have this function performing my conversion:
fromDateToString(date: Date) : String {
let dateAsString = date.toISOString().substr(0, 19)
console.log(dateAsString);
return dateAsString;
}
As you can see it take a Date object containing the following value:
Wed Feb 08 2017 07:00:00 GMT-0800 (Ora standard del Pacifico USA)
and, in theory it have to convert this date in the following string format:
2017-02-08T07:00:00"
But I am finding a strange behavior on the time !!! The generated string is not the previous one but it is:
2017-02-08T15:00:00"
The generated time section is not 07:00:00 but it is 15:00:00
Why? What is wrong? What am I missing? How can I fix this issue?

The value isn't wrong; you're disregarding the timezone. toISOString returns a string written in UTC with Z at the end saying it's in UTC. You're stripping off the part of the string saying what timezone it's in.
If you like, you can get that string in local time instead by subtracting the timezone offset:
function fromDateToString(date/*: Date*/)/* : String*/ {
date = new Date(+date);
date.setTime(date.getTime() - (date.getTimezoneOffset() * 60000));
let dateAsString = date.toISOString().substr(0, 19);
return dateAsString;
}
console.log(fromDateToString(new Date()));
Just beware that your code using that string handles it as a local time, not UTC.

2017-02-08T15:00:00 -> this is UTC date (ISO) [UTC has 0:00 offset]
2017-02-08T07:00:00 -> this is GMT-0800
so if we convert 2017-02-08T07:00:00 to UTC we need to add 8:00 hours so 7 + 8 = 15 so its giving 2017-02-08T15:00:00
You directly cannot ignore timezone offset without adding/subtracting.

That happens because the EcmaScript algorithm for generating an ISO string always generates it with the UTC+0 timezone. You don't need (and shouldn't) modify the Date object. Here's an algorithm to get a ISO string with the local timezone:
let toLocalISOString;
{
const pad = function pad(str) {
return String(str).padStart(2, "0");
}
toLocalISOString = function toLocalISOString(date) {
const tzOffset = date.getTimezoneOffset(),
tzPlus = tzOffset >= 0;
return date.getFullYear() +
'-' + pad(date.getMonth() + 1) +
'-' + pad(date.getDate()) +
'T' + pad(date.getHours()) +
':' + pad(date.getMinutes()) +
':' + pad(date.getSeconds()) +
'.' + (date.getMilliseconds() / 1000).toFixed(3).slice(2, 5) +
(tzPlus ? "+" + pad(tzOffset / 60) : "-" + pad((tzOffset / 60).toString().slice(1))) +
":" + pad((tzOffset % 60).toFixed(0));
};
}

Date.toISOString() but local time instead of UTC

Let's say we have this datetime:
var d = new Date("Sat Jul 21 2018 14:00:00 GMT+0200");
Exporting it as a string (console.log(d)) gives inconsistent results among browsers:
Sat Jul 21 2018 14:00:00 GMT+0200 (Paris, Madrid (heure d’été)) with Chrome
Sat Jul 21 14:00:00 UTC+0200 2018 with Internet Explorer, etc.
so we can't send datetime to a server with an unconsistent format.
The natural idea then would be to ask for an ISO8601 datetime, and use d.toISOString(); but it gives the UTC datetime: 2018-07-21T12:00:00.000Z whereas I would like the local-timezone time instead:
2018-07-21T14:00:00+0200
or
2018-07-21T14:00:00
How to get this (without relying on a third party dependency like momentjs)?
I tried this, which seems to work, but isn't there a more natural way to do it?
var pad = function(i) { return (i < 10) ? '0' + i : i; };
var d = new Date("Sat Jul 21 2018 14:00:00 GMT+0200");
Y = d.getFullYear();
m = d.getMonth() + 1;
D = d.getDate();
H = d.getHours();
M = d.getMinutes();
S = d.getSeconds();
s = Y + '-' + pad(m) + '-' + pad(D) + 'T' + pad(H) + ':' + pad(M) + ':' + pad(S);
console.log(s);

There is limited built-in support for formatting date strings with timezones in ECMA-262, there is either implementation dependent toString and toLocaleString methods or toISOString, which is always UTC. It would be good if toISOString allowed a parameter to specify UTC or local offset (where the default is UTC).
Writing your own function to generate an ISO 8601 compliant timestamp with local offset isn't difficult:
function toISOLocal(d) {
var z = n => ('0' + n).slice(-2);
var zz = n => ('00' + n).slice(-3);
var off = d.getTimezoneOffset();
var sign = off > 0? '-' : '+';
off = Math.abs(off);
return d.getFullYear() + '-'
+ z(d.getMonth()+1) + '-' +
z(d.getDate()) + 'T' +
z(d.getHours()) + ':' +
z(d.getMinutes()) + ':' +
z(d.getSeconds()) + '.' +
zz(d.getMilliseconds()) +
sign + z(off/60|0) + ':' + z(off%60);
}
console.log(toISOLocal(new Date()));

The trick is to adjust the time by the timezone, and then use toISOString(). You can do this by creating a new date with the original time and subtracting by the timezone offssetfrom the original time:
var d = new Date("Sat Jul 21 2018 14:00:00 GMT+0200");
var newd = new Date(d.getTime() - d.getTimezoneOffset()*60000);
console.log(newd.toISOString()); // 2018-07-21T22:00:00.000Z
Alternatively, you can simply adjust the original date variable:
var d = new Date("Sat Jul 21 2018 14:00:00 GMT+0200");
d = new Date(d.getTime() - d.getTimezoneOffset()*60000);
console.log(d.toISOString()); // 2018-07-21T22:00:00.000Z
For your convenience, the result from .getTime() is the number of milliseconds since 1 January 1970. However, getTimezoneOffset() gives a time zone difference from UTC in minutes; that’s why you need to multiply by 60000 to get this in milliseconds.
Of course, the new time is still relative to UTC, so you’ll have to ignore the Z at the end:
d = d.slice(0,-1); // 2018-07-21T22:00:00.000

My version:
// https://stackoverflow.com/questions/10830357/javascript-toisostring-ignores-timezone-offset/37661393#37661393
// https://stackoverflow.com/questions/49330139/date-toisostring-but-local-time-instead-of-utc/49332027#49332027
function toISOLocal(d) {
const z = n => ('0' + n).slice(-2);
let off = d.getTimezoneOffset();
const sign = off < 0 ? '+' : '-';
off = Math.abs(off);
return new Date(d.getTime() - (d.getTimezoneOffset() * 60000)).toISOString().slice(0, -1) + sign + z(off / 60 | 0) + ':' + z(off % 60);
}
console.log(toISOLocal(new Date()));

i have found a solution which has worked for me.
see this post: Modifying an ISO Date in Javascript
for myself i tested this with slight modification to remove the "T", and it is working. here is the code i am using:
// Create date at UMT-0
var date = new Date();
// Modify the UMT + 2 hours
date.setHours(date.getHours() + 2);
// Reformat the timestamp without the "T", as YYYY-MM-DD hh:mm:ss
var timestamp = date.toISOString().replace("T", " ").split(".")[0];
and an alternative method is stipulate the format you need, like this:
// Create the timestamp format
var timeStamp = Utilities.formatDate(new Date(), "GMT+2", "yyyy-MM-dd' 'HH:mm:ss");
note: these are suitable in locations that do not have daylight saving changes to the time during the year
it has been pointed out that the above formulas are for a specific timezone.
in order to have the local time in ISO format, first specify suitable Locale ("sv-SE" is the closest and easiest to modify), then make modification (change the space to a T) to be same as ISO format. like this:
var date = new Date(); // Create date
var timestamp = date.toLocaleString("sv-SE").replace(" ", "T").split(".")[0]; // Reformat the Locale timestamp ISO YYYY-MM-DDThh:mm:ss
References:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleString)
https://www.w3schools.com/Jsref/jsref_tolocalestring.asp
https://www.w3schools.com/Jsref/tryit.asp?filename=tryjsref_tolocalestring_date_all

Converting any kind of date format to MM\DD\YYYY

I am converting this 2 sets of date to the format MM\DD\YYYY
1.Thu Aug 31 15:00:00 GMT+08:00 2017
2017-08-09
When I'm converting the 1st one I use this code.
var STD_Date = STD_data[i][4]; //<----This is where the date comes.
var date = convertDate(STD_Date);
var datearray = date.split("/");
var New_STDDate = datearray[1] + '/' + datearray[0] + '/' + datearray[2];
This is the function convertDate()
function convertDate(inputFormat) {
function pad(s) { return (s < 10) ? '0' + s : s; }
var d = new Date(inputFormat);
return [pad(d.getDate()), pad(d.getMonth()+1), d.getFullYear()].join('/');
}
This is how I format the second one.
This is the function
var toMmDdYy = function(input) {
var ptrn = /(\d{4})\-(\d{2})\-(\d{2})/;
if(!input || !input.match(ptrn)) {
return null;
}
return input.replace(ptrn, '$2/$3/$1');
};
This is how I use it.
var startdate = form.startdate //<--- comes from HTML Picker (Format "YYYY-MM-DD")
toMmDdYy(startdate)
My question is this how can I have a function that will format the date whether it is the 1st or the 2nd one?
Convert_TimeStamp_Date(){
//This is where to code will go to convert
//to MM\DD\YYYY
}
//Then call it
var startdate = "2017-08-08"
var timestamp = "Thu Aug 31 15:00:00 GMT+08:00 2017"
Convert_TimeStamp_Date(startdate);
Convert_TimeStamp_Date(timestamp);
//both of them the output must be "MM\DD\YYYY"
This is the current code but looking forward for a better one. WORKING
//Time Stamp to MM\DD\YYYY
function convertDate(inputFormat) {
function pad(s) { return (s < 10) ? '0' + s : s; }
var d = new Date(inputFormat);
var chopdate = [pad(d.getDate()), pad(d.getMonth()+1), d.getFullYear()].join('/');
var datearray = chopdate.split("/");
var newdate = datearray[1] + '/' + datearray[0] + '/' + datearray[2];
return newdate;
}
//YYYY-MM-DD tp MM\DD\YYYY
var toMmDdYy = function(input) {
var ptrn = /(\d{4})\-(\d{2})\-(\d{2})/;
if(!input || !input.match(ptrn)) {
return null;
}
return input.replace(ptrn, '$2/$3/$1');
};
//Convert Date based on input to MM\DD\YYYY
function ConverSpedDate(input){
if( input.lenght > 10 ) return toMmDdYy(input);
return convertDate(input);
}

This should work
convertDate = function( input ){
if( input.lenght > 10 ) return convertDate( input );
return toMmDdYy( input );
}

You can test each pattern and reformat accordingly. Your reformatting functions appear to be cumbersome and error prone, consider the following:
var startdate = "2017-08-23"
var timestamp = "Thu Aug 31 15:00:00 GMT+08:00 2017"
function reformatTimestamp(s) {
if (/\d{4}-\d\d-\d\d/.test(s)) {
return reformatISOtoMDY(s);
} else if (/[a-z]{3} [a-z]{3} \d\d \d\d:\d\d:\d\d \w{3}\+\d\d:\d\d \d{4}/i.test(s)) {
return reformatCustomToMDY(s);
}
}
// Reformat YYYY-MM-DD to MM\DD\YYYY
function reformatISOtoMDY(s) {
var b = s.split(/\D/);
return b[1] + '\' + b[2] + '\' + b[0];
}
function reformatCustomToMDY(s) {
var months = '. jan feb mar apr may jun jul aug sep oct nov dec'.split(' ');
var b = s.split(/ /);
return ('0' + months.indexOf(b[1].toLowerCase())).slice(-2) +
'\' + ('0' + b[2]).slice(-2) + '\' + b[5];
}
console.log(reformatTimestamp(startdate))
console.log(reformatTimestamp(timestamp))
The format MM\DD\YYYY is unusual and likely to confuse.

As you've tagged this as a GAS question, have you looked at Utilities.formatDate()? Documentation here, but in short it takes 3 parameters: a date object, a time-zone string & a format string. The TZ & format are taken from the Java SE SimpleDateFormat class.
In your instance, try this:
var ts = "Thu Aug 31 15:00:00 GMT+08:00 2017";
var d = new Date(ts);
Logger.log(Utilities.formatDate(d, "GMT+08:00", "MM/dd/yyyy")); // logs 08/31/2017
Note that you will have to set the time-zone in the output yourself. You could extract it from the timestamp via a regex, for example. As the JS Date primitive is milliseconds 1970-01-01T00:00:00 UTC, you can set your output TZ to suit your needs.
I also +1 the recommendations to stick to ISO date & time formats: MM/dd/yyyy absent locale information is just asking for trouble.

ISO 8601 not retaining timezone?

i am using the timeago Jquery plugin to output strings like "5 mins ago" etc.
The plugin uses ISO 8601 date format.
I have a Date object which looks like this in console:
Sat Jun 15 2013 07:16:23 GMT+0530 (India Standard Time)
To convert it into ISO 8601 I do this:
date = date.toISOString();
Now it looks like this in the console:
2013-06-15T01:46:23Z
Apparently, the time zone has been set to UTC ( Z stand for UTC ).
This messes up with timeago plugin as everything is now in UTC, not in the local timezone.
I tried this:
Date.prototype.toISOStringfix = function() {
function pad(n) { return n < 10 ? '0' + n : n }
return this.getUTCFullYear() + '-'
+ pad(this.getUTCMonth() + 1) + '-'
+ pad(this.getUTCDate()) + 'T'
+ pad(this.getUTCHours()) + ':'
+ pad(this.getUTCMinutes()) + ':'
+ pad(this.getUTCSeconds()) + 'Z';
};
However, I get the same result.
Why does this happen? How can I fix it?

Date() converts certain date strings to local time

I'm trying to compare two date strings for equality by wrapping them with the Date() object. I live in Seattle and for some reason, the second date string is converted to PST and then rendered in GMT, resulting in the below:
new Date("January 1, 2012")
>>> Sun Jan 01 2012 00:00:00 GMT-0800 (PST)
new Date("2012-01-01")
>>> Sat Dec 31 2011 16:00:00 GMT-0800 (PST)
Try the above in the chrome console and you should get the same results.
How do I get Date to evaluate the second statement as GMT instead of PST?

Do not use the Date object to parse date strings, it is specified as implementation dependent in ECMAScript ed 3 and doesn't work consistently across browsers. One format of ISO8601 date string is specified in ES5, but that doesn't work consistently either. Manually parse the string.
A couple of functions to convert to and from UTC ISO8601 strings:
if (!Date.prototype.toUTCISOString) {
Date.prototype.toUTCISOString = function() {
function addZ(n) {
return (n<10? '0' : '') + n;
}
function addZ2(n) {
return (n<10? '00' : n<100? '0' : '') + n;
}
return this.getUTCFullYear() + '-' +
addZ(this.getUTCMonth() + 1) + '-' +
addZ(this.getUTCDate()) + 'T' +
addZ(this.getUTCHours()) + ':' +
addZ(this.getUTCMinutes()) + ':' +
addZ(this.getUTCSeconds()) + '.' +
addZ2(this.getUTCMilliseconds()) + 'Z';
}
}
if (!Date.parseUTCISOString) {
Date.parseUTCISOString = 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;
}
}
var s = '2012-05-21T14:32:12Z'
var d = Date.parseUTCISOString(s);
alert('Original string: ' + s +
'\nEquivalent local time: ' + d +
'\nBack to UTC string: ' + d.toUTCISOString());

Taking robg's advice you might look at DateJS or moment.js

That's because of your time zone, you are 8:00 hours late to the "2012-01-01", so its showing like that, for me i got this
new Date("January 1, 2012")
Sun Jan 01 2012 00:00:00 GMT+0530 (IST)
new Date("2012-01-01")
Sun Jan 01 2012 05:30:00 GMT+0530 (IST)