Develop Reference

How can I set my local date in javaScript

I'm using this code to get the difference between today date and my data date from database
I notice every day at 3 pm . next day start
( for example if today is 20 . at 3 pm the date will be 21 )
const oneDay = 24 * 60 * 60 * 1000;
var serverDate = new Date(value)
let todayDate = new Date()
const difference = Math.round(Math.abs((todayDate - serverDate) / oneDay));
return difference
How can I set my local date or there is better way to solve this problem

You can get your local time by passing your location with localeString.
var asiaTime = new Date().toLocaleString("en-US", { timeZone: "Asia/Shanghai"
});
asiaTime = new Date(asiaTime);
console.log('Asia time in string: ' + asiaTime.toLocaleString())
console.log('Asia time in Date format', asiaTime)
var aestTime = new Date().toLocaleString("en-US", {timeZone:
"Australia/Brisbane"});
aestTime = new Date(aestTime);
console.log('AEST time: '+aestTime.toLocaleString())
console.log('AEST time in Date format', aestTime)
var indiaTime = new Date().toLocaleString("en-US", {timeZone:
"Asia/Kolkata"});
indiaTime = new Date(indiaTime);
console.log('India time: '+indiaTime.toLocaleString())
console.log('Inida time in Date format', indiaTime)
Hope this Helps . GOOD LUCK.

If you need to find the difference between the current and your DB date run the below code.
var d = new Date();
var currentDate = moment(d.toLocaleString(),'M/D/YYYY');
var systemDate = moment('2/20/2019','M/D/YYYY');
var diffDays = currentDate.diff(systemDate, 'days');
console.log("diffDays",diffDays);
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.18.1/moment.min.js"></script>

Fastest method of building a timestamp of the current hour

I'm looking for the fastest method to build a timestamp which represents the current hour starting from the current instant (in general, starting from a timestamp)
Currently I'm doing the following:
var d = new Date();
var year = d.getUTCFullYear();
var month = d.getUTCMonth();
var day = d.getUTCDate();
var hour = d.getUTCHours();
d = new Date(year, month, day, hour);
console.log(d);
console.log(d.getTime());
Is it possible to avoid the second invocation of Date?

If I understand you correctly you want the timestamp of the beginning of the current hour. Then you could simply set the minutes and seconds to 0 in your first Date Object:
var d = new Date();
d.setMinutes(0,0);
console.log(d);
console.log(d.getTime());
You could make it a oneliner, since setMinutes() already returns a timestamp:
var timestamp = new Date().setMinutes(0,0);

Not sure why you're doing that twice, you really don't need to.
var d = new Date();
console.log(d.getHours());
// or
console.log(d.getTime() );

JavaScript : How do i set plus or minus 60 days daterange from today?

I need to pass startdate and enddate parameters to a webservice to fetch the response which range is from plus or minus 60 days from the current date. So what value i need to pass it in the StartDate and EndDate param of javascript? My Client Side App is build on JavaScript/AngularJs.

You can do this:
var todaysDate = new Date();
var startDate = new Date();
var endDate = new Date();
startDate.setDate(todaysDate.getDate() - 60);
endDate.setDate(todaysdate.getDate() + 60);

have a look at momentjs http://momentjs.com/ this is an excellent angular wrapper for moment https://github.com/gdi2290/angular-momentjs. always worth adding to your project when dealing with dates and times

Unix timestamp version:
var currentUTC = new Date().valueOf()
var sixtyDays = 60*24*60*60*1000
var startDate = currentUTC - sixtyDays
var endDate = currentUTC + sixtyDays

Get time difference in javascript ISO format

I have a datetime in ISO format i.e.
2012-06-26T01:00:44Z
I want to get the time difference from current time. How can I achieve this using javascript or javascript library Date.js or jquery

This will give you the difference in milliseconds, you can then format it as you want
var diff = new Date("2012-06-26T01:00:44Z") - new Date();

Try this:
var someDate = new Date("2012-06-26T01:00:44Z");
var now = new Date();
var one_day = 1000 * 60 * 60 * 24;
var diff = Math.ceil((someDate.getTime()-now .getTime())/(one_day))
alert(diff)
Example fiddle
You can obviously amend the one_day variable to get the difference in the unit you require.

I would suggest converting ISO format to something that works cross browser.
Try this,
var d = "2012-06-26T01:00:44Z";
var someDate = new Date(d.replace(/-/g,'/').replace('T',' ').replace('Z',''));
alert(someDate - new Date());
Edit:
I guess, you need pretty time
Try this awesome code
Edit 2:
You needed reverse, so try this instead
var old_date = new Date();
alert('Old date: ' + old_date.toGMTString())
var new_date = new Date(old_date.setMinutes(old_date.getMinutes() - 5));
alert('Date 5 minutes before: ' + new_date.toGMTString());
If you need timestamp,
alert(new_date.getTime());

in order to format date you can use this function to get the desire format of the date and you can easily change the position of day , month and year.
function convertFormat(inputDate)
var date = new Date(inputDate);
var day = date.getDate();
var month = date.getMonth()+1;
var year = date.getFullYear();
var fullYear = year + '/' + month + '/' + day
return fullYear;

Convert Returned String (YYYYMMDD) to Date

I have a string that contains 8 digits that represent a date. For example:
20120515
I'd like to compare it with today's date, created in this manner:
var currentDate = new Date();
How can I convert the "8 digit date string" to a suitable date format in order to compare it to currentDate?

Use the substring method and substring off 4 elements and assign it to your new date for the year. Then substring off two elements at a time and store the month and date accordingly.
var dateString = "20120515";
var year = dateString.substring(0,4);
var month = dateString.substring(4,6);
var day = dateString.substring(6,8);
var date = new Date(year, month-1, day);
var currentDate = new Date();
Now you can compare the two dates with the normal operators.

If you want a small date library you can use moment.js.
var a = moment("20120515", "YYYYMMDD");
// then use any of moment's manipulation or display functionality
a.format("MMM Do YYYY"); // May 15th 2012
a.fromNow(); // 14 hours ago
a.calendar(); // Today at 12:00 AM

To correctly handle the local time zone, it must explicitly summed to the calculated time
function dateStringToDate(dateString) {
try {
var year = dateString.substring(0, 4);
var month = dateString.substring(4, 6);
var day = dateString.substring(6, 8);
var date = new Date(year, month - 1, day);
const offset = date.getTimezoneOffset()
date = new Date(date.getTime() - (offset * 60 * 1000));
return date;
} catch (error) {
return null;
}
}
function dateStringToDate(dateString) {
try {
var year = dateString.substring(0, 4);
var month = dateString.substring(4, 6);
var day = dateString.substring(6, 8);
var date = new Date(year, month - 1, day);
const offset = date.getTimezoneOffset()
date = new Date(date.getTime() - (offset * 60 * 1000));
return date;
} catch (error) {
return null;
}
}
console.log(dateStringToDate("20211212"))
console.log(dateStringToDate("20211213"))
console.log(dateStringToDate("20211214"))

...some other "one-liner" ways to accomplish this:
(They take a value like dts='20020704'; and return date object [dt].)
var dt=new Date(dts.slice(0,4), (dts[4]+dts[5])-1, dts[6]+dts[7]);
...or...
var m=dts.match(/(....)(..)(..)/), dt=new Date(m[1],m[2]-1,m[3]);
...or...
var m=dts.match(/.{1,2}/g), dt=new Date(m[0]+m[1],m[2]-1,m[3]);
The last one's shortest, but the first is probably most efficient, since it doesn't use regex (but that's irrelevant, unless you're processing LOTS of data using this). I like the middle one best since it's easy to see what's happening.