Develop Reference

Javascript Date parsing returning strange results in Chrome

I observed some strange Date behaviour in Chrome (Version 74.0.3729.131 (Official Build) (64-bit)).
Following javascript was executed in the Chrome Dev Console:
new Date('1894-01-01T00:00:00+01:00')
// result: Mon Jan 01 1894 00:00:00 GMT+0100 (Central European Standard Time)
new Date('1893-01-01T00:00:00+01:00')
// result: Sat Dec 31 1892 23:53:28 GMT+0053 (Central European Standard Time)
I have already read about non standard date parsing via the Date ctor in different browsers, although providing valid ISO8601 values.
But this is more than strange o_o
In Firefox (Quantum 66.0.3 (64-Bit)) the same calls result in expected Date objects:
new Date('1894-01-01T00:00:00+01:00')
// result: > Date 1892-12-31T23:00:00.000Z
new Date('1893-01-01T00:00:00+01:00')
// result: > Date 1893-12-31T23:00:00.000Z
Is this a bug in Chrome?
My input is valid ISO8601 i guess?
The most important question is, how do I fix this? (hopefully without parsing the input string myself)

Okay, seems like this behaviour cannot be avoided, so you should parse dates manually. But the way to parse it is pretty simple.
If we are parsing date in ISO 8601 format, the mask of date string looks like this:
<yyyy>-<mm>-<dd>T<hh>:<mm>:<ss>(.<ms>)?(Z|(+|-)<hh>:<mm>)?
1. Getting date and time separately
The T in string separates date from time. So, we can just split ISO string by T
var isoString = `2019-05-09T13:26:10.979Z`
var [dateString, timeString] = isoString.split("T")
2. Extracting date parameters from date string
So, we have dateString == "2019-05-09". This is pretty simple now to get this parameters separately
var [year, month, date] = dateString.split("-").map(Number)
3. Handling time string
With time string we should make more complex actions due to its variability.
We have timeString == "13:26:10Z"
Also it's possible timeString == "13:26:10" and timeString == "13:26:10+01:00
var clearTimeString = timeString.split(/[Z+-]/)[0]
var [hours, minutes, seconds] = clearTimeString.split(":").map(Number)
var offset = 0 // we will store offset in minutes, but in negation of native JS Date getTimezoneOffset
if (timeString.includes("Z")) {
// then clearTimeString references the UTC time
offset = new Date().getTimezoneOffset() * -1
} else {
var clearOffset = timeString.split(/[+-]/)[1]
if (clearOffset) {
// then we have offset tail
var negation = timeString.includes("+") ? 1 : -1 // detecting is offset positive or negative
var [offsetHours, offsetMinutes] = clearOffset.split(":").map(Number)
offset = (offsetMinutes + offsetHours * 60) * negation
} // otherwise we do nothing because there is no offset marker
}
At this point we have our data representation in numeric format:
year, month, date, hours, minutes, seconds and offset in minutes.
4. Using ...native JS Date constructor
Yes, we cannot avoid it, because it is too cool. JS Date automatically match date for all negative and too big values. So we can just pass all parameters in raw format, and the JS Date constructor will create the right date for us automatically!
new Date(year, month - 1, date, hours, minutes + offset, seconds)
Voila! Here is fully working example.
function convertHistoricalDate(isoString) {
var [dateString, timeString] = isoString.split("T")
var [year, month, date] = dateString.split("-").map(Number)
var clearTimeString = timeString.split(/[Z+-]/)[0]
var [hours, minutes, seconds] = clearTimeString.split(":").map(Number)
var offset = 0 // we will store offset in minutes, but in negation of native JS Date getTimezoneOffset
if (timeString.includes("Z")) {
// then clearTimeString references the UTC time
offset = new Date().getTimezoneOffset() * -1
} else {
var clearOffset = timeString.split(/[+-]/)[1]
if (clearOffset) {
// then we have offset tail
var negation = timeString.includes("+") ? 1 : -1 // detecting is offset positive or negative
var [offsetHours, offsetMinutes] = clearOffset.split(":").map(Number)
offset = (offsetMinutes + offsetHours * 60) * negation
} // otherwise we do nothing because there is no offset marker
}
return new Date(year, month - 1, date, hours, minutes + offset, seconds)
}
var testDate1 = convertHistoricalDate("1894-01-01T00:00:00+01:00")
var testDate2 = convertHistoricalDate("1893-01-01T00:00:00+01:00")
var testDate3 = convertHistoricalDate("1894-01-01T00:00:00-01:00")
var testDate4 = convertHistoricalDate("1893-01-01T00:00:00-01:00")
console.log(testDate1.toLocaleDateString(), testDate1.toLocaleTimeString())
console.log(testDate2.toLocaleDateString(), testDate2.toLocaleTimeString())
console.log(testDate3.toLocaleDateString(), testDate3.toLocaleTimeString())
console.log(testDate4.toLocaleDateString(), testDate4.toLocaleTimeString())
Note
In this case we are getting Date instance with all its own values (like .getHours()) being normalized, including timezone offset. The testDate1.toISOString will still return weird result. But if you are working with this date, it will probably 100% fit your needings.
Hope that helped :)

This might be the case when all browsers follow their own standards for encoding date formats (but I am not sure on this part). Anyways a simple fix for this is to apply the toISOString method.
const today = new Date();
console.log(today.toISOString());

Javascript Date Comparison not behaving as expected

I am getting a SQL date - NOT datetime - object pushed into my Javascript code, and I need to see whether it's before today or not. Here is the code I have (the relevant part):
todaysDate = new Date();
todaysDate.setHours(0,0,0,0);
var date = Date.parse(row[3]);
// date.setHours(0,0,0,0);
if (date < todaysDate) {
alert("date is before today");
dueDate = '<small class="text-danger">';
} else {
alert("date is after today");
dueDate = '<small class="text-muted">';
}
row[3] is the source of the SQL date. So, this works fine for everything except dates that are today. Without the commented line, it thinks that anything with today's date is in the past. With the commented line, my code breaks. Any thoughts as to how to fix this? Not sure what I'm doing wrong.
Thanks!

If your date string is like "2016-04-10" and your time zone is west of GMT, say -04:00, then in browsers compliant with ECMAScript 2016 you will get a Date for "2016-04-09T19:00:00-0400".
When you create a Date using new Date() and set the hours to zero (assuming it's 10 April where you are), you'll get a Date for "2016-04-10T00:00:00-0400".
So when compared they have different time values.
What you need is to either treat the string you get from the database as local, or get the UCT date where you are, so:
var dateString = '2016-04-10';
var parsedDate = new Date(dateString);
var todayUTCDate = new Date();
todayUTCDate.setUTCHours(0,0,0,0);
document.write(parsedDate + '<br>' + todayUTCDate);
But not all browsers parse strings according to ECMAScript 2015 so they should always be manually parsed. Use a library, or write a small function, e.g.
// Parse date string in format 'yyyy-mm-dd' as local date
function parseISOLocal(s) {
var b = s.split(/\D/);
return new Date(b[0], b[1]-1, b[2]);
}
and replace:
var date = Date.parse(row[3]);
with:
var date = parseISOLocal(row[3]);
and then in the comparison, compare the time values:
if (+date < +todaysDate) {
or
if (date.getTime() < todaysDate.getTime()) {

Use getTime() of date object.
The getTime() method returns the number of milliseconds between midnight of January 1, 1970 and the specified date.
You can compare miliseconds and do your operations
date.getTime() > todaysDate.getTime()
Also be sure that Date.parse is returning a valid date.

PHP, javascript, jquery, setting hour only

I have created a small function that i need on my site successfully in php. But i now realise i actually need this in javascript or jquery as PHP will only excute this code on load.. i need this function to work with onchange on a select. The code below is my function.. Can anyone point out where i start to convert this into js/jquery like code:
function setTrnTime ($hr, $journeyTime){
date_default_timezone_set('GMT');
//convert current hour to time format hour
$currentHour = (date("H", mktime($hr)));
// Journey time in hours
$journey = $journeyTime
$journey = $journey/60; // Get hours
$journey = ceil($journey); // Round off to next hour i.e. 3 hours 20mins is now 4 hours
// New Hours
$NewHour = (date("H", mktime($journey)));
$Newhour = $NewHour*60*60; // convert to seconds
// Final hour is Current Hour - JourneyTime (Hours)
$trnHour = (date('H', mktime($currentHour-$NewHour)));
return $trnHour;
}
With the code above, if i pass two values 06, 60: that would mean my answer would be 05. e.g. 06 is 6am. 60 is 60mins.. so 6am - 60mins = 5am.

You can do the same in javascript using the Date object, see info here
https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Date
EDITED: Added some code, also not even using the Date object.
But do you need something that complex, doesn't the following do what you are after with less steps.
http://jsfiddle.net/WWTDc/

If hr is a Date object, then it's very simple. Otherwise you can create a Date object and set its hour:
//! \param[in] hr Date object or hour (0--23)
//! \param[in] journeyTime journey time in minutes.
function setTrnTime(hr,journeyTime){
var end;
if(typeof(hr) === 'number'){
end = new Date();
end.setHours(hr);
}
else
end = hr;
return (new Date(end - journeyTime*60*1000)).getHours();
}
This will return the hour (demonstration).

See here for information about Date object in JavaScript.

Relative Time jQuery Plugin (like Twitter, FB, etc) Breaks in Safari?

Works in all browsers except Firefox, any ideas?
(function($){
$.relativetime = function(options) {
var defaults = {
time:new Date(),
suffix:'ago',
prefix:''
};
options = $.extend(true, defaults, options);
//Fixes NaN in some browsers by removing dashes...
_dateStandardizer = function(dateString){
modded_date = options.time.toString().replace(/-/g,' ');
return new Date(modded_date)
}
//Time object with all the times that can be used throughout
//the plugin and for later extensions.
time = {
unmodified:options.time, //the original time put in
original:_dateStandardizer(options.time).getTime(), //time that was given in UNIX time
current:new Date().getTime(), //time right now
displayed:'' //what will be shown
}
//The difference in the unix timestamps
time.diff = time.current-time.original;
//Here we save a JSON object with all the different measurements
//of time. "week" is not yet in use.
time.segments = {
second:time.diff/1000,
minute:time.diff/1000/60,
hour:time.diff/1000/60/60,
day:time.diff/1000/60/60/24,
week:time.diff/1000/60/60/24/7,
month:time.diff/1000/60/60/24/30,
year:time.diff/1000/60/60/24/365
}
//Takes a string and adds the prefix and suffix options around it
_uffixWrap = function(str){
return options.prefix+' '+str+' '+options.suffix;
}
//Converts the time to a rounded int and adds an "s" if it's plural
_niceDisplayDate = function(str,date){
_roundedDate = Math.round(date);
s='';
if(_roundedDate !== 1){ s='s'; }
return _uffixWrap(_roundedDate+' '+str+s)
}
//Now we loop through all the times and find out which one is
//the right one. The time "days", "minutes", etc that gets
//shown is based on the JSON time.segments object's keys
for(x in time.segments){
if(time.segments[x] >= 1){
time.displayed = _niceDisplayDate(x,time.segments[x])
}
else{
break;
}
}
//If time.displayed is still blank (a bad date, future date, etc)
//just return the original, unmodified date.
if(time.displayed == ''){time.displayed = time.unmodified;}
//Give it to em!
return time.displayed;
};
})(jQuery);
In Safari, this code returns the given date which my plugin date if it fails. This could happen due to a future date or an invalid date. However, I'm not sure as the time that is given is standard YY MM DD HH:mm:ss
Demo:
http://jsfiddle.net/8azeT/

I think the string used is wrong and then stripped of '-' very wrong:
'010111' - interpreted by FF as Jan 1 1911 (US FF)
Correct format is '01/01/2011' (US FF)
I wouldn't use this format at all as each country has it's own way of showing/ parsing dates.
The safest way to parse a string is probably to use:
'January 1, 2011 1:30:11 pm GMT'
but I would use a date object instead in the options and skip the string parsing to make sure the date is correct.
http://jsfiddle.net/8azeT/4/
Question is about Safari but content FF?

creating date from a timestring in javascript

I am new to javascript and am trying to compare two date values ,I am getting two time value strings in the format
06:30:47 AM
01:10:47 PM
I need to compare these to find out if the first one is less than the other.I couldn't figure out how to do this in javascript.Can someone help?
o.h

I do not think that the standard implementation can parse this. I would do something like this:
function toDate(dateString) {
var timeComponents = dateString.replace(/\s.*$/, '').split(':');
if (dateString.indexOf("PM") > -1) {
timeComponents[0] += 12;
}
var date = new Date();
date.setHours(timeComponents[0]);
date.setMinutes(timeComponents[1]);
date.setSeconds(timeComponents[2]);
return date;
}
if (toDate('06:30:47 AM') > toDate('01:10:47 PM')) {
// ...
}

JavaScript's specified date/time parsing, what you can rely upon cross-browser, is surprisingly limited. For a long time, there was no single string date format that was mandated in the spec, and as of the recent 5th edition spec, the only mandated format is ISO-8601 (and some subsets). You can't yet rely on browsers having implemented that part of the 5th edition spec.
So you have a couple of choices:
Parse the string yourself and use the Date constructor that takes the individual parts of the date as numbers, e.g. new Date(year, month, day, hour, minute, second, ...). (You need only specify as many of those as you want, so for instance new Date(2010, 9, 14) is September 14th, 2010.)
Use a library like Moment that's already done the work for you. Moment lets you specify the format to parse.

Use the Date object. Check this: http://www.w3schools.com/jsref/jsref_obj_date.asp
Try putting the two values in Date variables and do this:
if(var1.valueOf() > var2.valueOf())
{
//Do Something
}

If your times are always in the format 00:00:00 AM then
var a="06:30:47 AM";
var b="01:10:47 PM";
var at=parseInt(a.substring(0,8).replace(/(^0+|:)/g,""));
var bt=parseInt(b.substring(0,8).replace(/(^0+|:)/g,""));
if (a.charAt(9)=="P") {at=at+120000};
if (b.charAt(9)=="P") {bt=bt+120000};
if (at<bt) {
// a is smaller
}
else
{
// a is not smaller
};
..should be cross-browser and time/format safe.

I tried something like this
var ts1="06:30:47 AM";
var ts2="01:10:47 PM";
var ds=new Date().toDateString();
var d1=new Date(ds+" "+ts1);
var d2=new Date(ds+" "+ts2);
if (!(d2>d1)){
alert("d1 should be less than d2");
}
Is there something wrong with this?

// specific formatter for the time format ##:##:## #M
var formatToMiliseconds = function(t){
t = t.split(/[:\s]/);
t = ((t[0] * 3600000) + (t[1] * 60000) * (t[2] * 1000)); // To ms
t = t + (/PM/i.test(t[3]) ? 43200000 : 0); // adjust for AM/PM
return t;
}
var time01 = formatToMiliseconds('06:30:47 AM');
var time02 = formatToMiliseconds('01:10:47 PM');
alert(time01 > time02); // false
allert(time01 < time02); // true
As a bonus, your time is now more compatible with the Date object and other time calculations.