Develop Reference

Difference (in days) between two days in yyyy-mm-dd format?

Sorry if this has been asked before, but I haven't been able to find anything. Here's essentially what I'm trying to do:
new Date(response.departureDate).getTime() - new Date(response.arrivalDate).getTime()
I need to calculate the total number of days (will always be a whole integer) between an arrival and departure date. These dates are strings, structured as 'YYYY-MM-DD'.
How do I go about this?

You can use regexp OR a much simpler approach would be to become familiar with MomentJS API that lets you deal with dates in JS very smoothly (works in Node and browser)
http://momentjs.com/
It does add another tool to your toolbox, but as soon as you are manipulating dates, it is definetely worth it IMHO.
Way to go with MomentJS :
var depDate = moment(response.departureDate);
var arrDate = moment(response.arrivalDate);
var nbDays = depDate.diff(arrDate, 'days');

Look at the Miles' answer here
Just change it to:
function parseDate(str) {
var mdy = str.split('-')
return new Date(mdy[2], mdy[0]-1, mdy[1]);
}
function daydiff(first, second) {
return Math.round((second-first)/(1000*60*60*24));
}
and use:
daydiff(parseDate(response.departureDate), parseDate(response.arrivalDate));

You can use RegEx to change them.
new Date(response.departureDate.replace(/-/g, "/")).getTime()
- new Date(response.arrivalDate.replace(/-/g, "/")).getTime()
So the RegEx .replace(/-/g, "/") will replace all the - to /, and JavaScript will be able to read it right.

I hope this example help for you
Apart from .diff(), you could also use moment durations: http://momentjs.com/docs/#/durations/
Example Fiddle: https://jsfiddle.net/abhitalks/md4jte5d/
Example Snippet:
$("#btn").on('click', function(e) {
var fromDate = $('#fromDate').val(),
toDate = $('#toDate').val(),
from, to, druation;
from = moment(fromDate, 'YYYY-MM-DD'); // format in which you have the date
to = moment(toDate, 'YYYY-MM-DD'); // format in which you have the date
/* using duration */
duration = moment.duration(to.diff(from)).days(); // you may use duration
/* using diff */
//duration = to.diff(from, 'days') // alternatively you may use diff
/* show the result */
$('#result').text(duration + ' days');
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.11.1/moment.min.js"></script>
From: <input id="fromDate" type='date' />
To: <input id="toDate" type='date' />
<button id="btn">Submit</button><hr />
<p id="result"></p>

You can use something like this
function countDays(date1, date2)
{
var one_day=1000*60*60*24;
return Math.ceil((date1.getTime()- date2.getTime()) /one_day);
}
countDays(new Date(response.departureDate), new Date(response.arrivalDate));

How to get the Australian Time Zone using Javascript? (Not JQuery)

I am trying to help a friend to get the Australian Time Zone for the University Assignment and finding difficulty.
Could someone point us in the right direction?
Thank you!
<script>
function Timezone() {
var x = new Date();
var currentTimeZoneOffsetInHours = x.getTimezoneOffset() / 60;
document.getElementById("add").innerHTML = currentTimeZoneOffsetInHours;
}
</script>
<p id="add"></p>

You simply use
let AuDate = new Date().toLocaleString("en-US", {timeZone: "Australia/Sydney"});

By looking at your code, looks like you are trying to get the current date and time of an Australian timezone. Lets say you want Australian Eastern Standard Time (AEST) and you want the date displayed how they would in Australia DD-MM-YYYY then do the following:
var timestamp_UTC = new Date();
var readable_timestamp_AEST = timestamp_UTC.toLocaleDateString("en-AU", {timeZone: "Australia/Sydney"}).replace(/\//g, "-") + ' ' + somestamp.toLocaleTimeString("en-AU", {timeZone: "Australia/Sydney"});
"en-AU" is the locales argument which tells the toLocalDateString to display the date as DD-MM-YYYY and the second argument is for options (timeZone is just one such possible option). Info about toLocalDateString function can be found here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleDateString
Here is some information about the Date() function https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date
Hope this clears up a few things around getting times and dates from the Date() function.

I think i understand what you mean. But before that i'd like to make 2 points:
1: The Timezone() function should be called somewhere.
<script>
function Timezone() {
var x = new Date();
var currentTimeZoneOffsetInHours = x.getTimezoneOffset() / 60;
document.getElementById("add").innerHTML = currentTimeZoneOffsetInHours;
}
Timezone();
</script>
2: The convention usually is that methods start with a lower case letter. Maybe updateTimezone() would be more appropriate.
Your question can be interpreted in 2 ways now:
you want your timezone's offset in hours and for this the code above should work. getTimezoneOffset() is the way to go.
you want a human readable name of your timezone, as you can see on my site currentmillis.com (in my case it says GTB Summer). You can look in my source code to see how i achieve this:
var s = date.toString();
var iOfP = s.indexOf('('); // index of parenthesis
if (iOfP < 0) {
s = s.substring(s.lastIndexOf(' ') + 1);
} else {
s = s.substring(iOfP+1, s.length-1);
}
if (s.length > 4 && s.lastIndexOf(" Time") == s.length-5){
s = s.substring(0, s.length-5);
}
timezoneM.innerHTML = s;
This works because when you call toString() on the date the result should contain the full name of your timezone: w3schools.com/jsref/jsref_tostring_date.asp

Convert 1 AM PST to local time in JavaScript?

We have a system script that runs everyday at 1 AM PST. We have users around the world. We want to provide a simple web page that uses JavaScript to show 1 AM PST in the user's local timezone. For instance, a user in New York City should see 4 AM PST as the time the system script will run.
The PST time format is HH:MM DD.YYYY.
This only needs to work on mobile Safari.
What's the best way to do this?

The code would something like this:
alert(new Date(your_pst_server_time).toLocaleString());

You can use the .getUTCHours() and .getTimezoneOffset() methods of the new Date() object. For the ease of use, I attached this new function to that object. It will accept a parameter that specifies the time format that gets returned.
Date.prototype.getLocalTime = function (format){
var date = new Date();
var finalTime = ((date.getUTCHours()-2))-(((date.getTimezoneOffset())/60));
if (format+'' != '24'){
if (finalTime < 0){ finalTime = finalTime + 24 }
}
else {
if (finalTime > 12){ finalTime = (finalTime - 12)+" PM" }
else { finalTime += " AM" }
}
return finalTime.toString();
}
With my CET timezone, calling new Date().getLocalTime('24') will return "10" and calling new Date().getLocalTime() (without parameters or a parameter that isn't "24") will return "10 AM".
Time Conversion Site to check timezones

This function is a reasonable first start, but would not cope with countries like India which have a time offset of x.5 hours (x hours + 30mins). Unfortunately you cannot just divide by 60 like that.

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.

the closest Sunday before given date with JavaScript

I need to know the date for last Sunday for given date in php & javascript
Let's have a function give_me_last_Sunday
give_me_last_Sunday('20110517') is 20110515
give_me_last_Sunday('20110604') is 20110529
The full backup is done on Sundays = weekly. If I want to restore daily backup I need full (weekly) and daily backup. I need to copy backup files before restoring to temp directory so I restoring daily backup I need to know what weekly backup file I need to copy along the daily file.
My thought was to get Julian representation (or something similar) for the given date and then subtract 1 and check if it is Sunday ... Not sure if this is the best idea and how to convert given date into something I can subtract.

Based on Thomas' effort, and provided the input string is exactly the format you specified, then:
function lastSunday(d) {
var d = d.replace(/(^\d{4})(\d{2})(\d{2}$)/,'$1/$2/$3');
d = new Date(d);
d.setDate(d.getDate() - d.getDay());
return d;
}
Edit
If I were to write that now, I'd not depend on the Date object parsing the string but do it myself:
function lastSunday(s) {
var d = new Date(s.substring(0,4), s.substring(4,6) - 1, s.substring(6));
d.setDate(d.getDate() - d.getDay());
return d;
}
While the format yyyy/mm/dd is parsed correctly by all browsers I've tested, I think it's more robust to stick to basic methods. Particularly when they are likely more efficient.

Ok so this is for JavaScript only. You have an input that you need to extract the month, date, and year from. The following is just partly an answer then on how to get the date:
<script type="text/javascript">
var myDate=new Date();
myDate.setFullYear(2011,4,16)
var a = myDate.getDate();
var t = myDate.getDay();
var r = a - t;
document.write("The date last Sunday was " + r);
</script>
So the setFullYear function sets the myDate to the date specified where the first four digits is the year, the next are is the month (0= Jan, 1= Feb.,...). The last one is the actually date. Then the above code gives you the date of the Sunday before that. I am guessing that you can add more code to get the month (use getMonth() method). Here are a few links that might be helpful
http://www.w3schools.com/js/js_obj_date.asp
http://www.w3schools.com/jsref/jsref_setFullYear.asp
http://www.w3schools.com/jsref/jsref_getMonth.asp
(You can probably find the other functions that you need)
I hope this helps a bit even though it is not a complete answer.

Yup and strtotime has been ported to JS for eg http://phpjs.org/functions/strtotime:554 here.

final code (big thanks to #Thomas & #Rob)
function lastSunday(d) {
var d = d.replace(/(^\d{4})(\d{2})(\d{2}$)/,'$1/$2/$3');
d = new Date(d);
d.setDate(d.getDate() - d.getDay());
year = d.getFullYear()+'';
month = d.getMonth()+1+'';
day = d.getDate()+'';
if ( month.length == 1 ) month = "0" + month; // Add leading zeros to month and date if required
if ( day.length == 1 ) day = "0" + day;
return year+month+day;
}