I have a Date object and I'm trying to add a year to the today's date. I also have to have a way to compare the date that's in the date object (newly made + one year) and today's date. How do I compare today's date with the date in the variable? The point is, I need to have a way to know if today's date is the same or greater to the expiration date, that way I could redirect users to a different location... thanks all!
here's my Date object
var expDate = new Date();
The basic JavaScript Date object has stuff built in to handle all of that natively.
For adding a year to your date simply do this:
var currentDate = new Date();
var futureDate = new Date(currentDate);
futureDate.setFullYear(futureDate.getFullYear() + 1);
That gets the current day as the date, and then creates a new date, based on today's date and sets the yea to the current year plus 1.
As for the comparison, simply use <, <=, >, >=, ==, and !=. JavaScript understands what to do with those operators when Date objects are involved and will compare the two dates appropriately.
On thing that I might suggest doing (since you only care about the actual date, and not the time element of the Date object, is add in this line of code after getting today's date:
currentDate.setHours(0, 0, 0, 0);
That will set the hour, minute, second, and millisecond values to 0, so that only the date is a factor when doing any comparisons.
For everything that you could ever need to know about the JavaScript Date object, check out here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date
Edit: Fixed syntax issue.
Related
This question is related to this question.
So if we construct a date using an ISO string like this:
new Date("2000-01-01")
Depending on what timezone we are in, we might get a different year and day.
I need to be able to construct dates in Javascript that that always have the correct year, day, and month indicated in a string like 2000-01-01, and based on the answer in one of the questions if we use back slashes instead like this:
const d = new Date("2000/01/01")
Then we will always get the right year, day, and month when using the corresponding date API methods like this:
d2.getDate();
d2.getDay();
d2.getMonth();
d2.getFullYear();
So I just wanted to verify that my understanding is correct?
Ultimately I need to be able to create Date instances like this for example:
const d3 = new Date('2010/01/01');
d3.setHours(0, 0, 0, 0);
And the time components should always be zero, and the year, month, and day should be the numbers specified in the string.
Thoughts?
I just did a quick test with this:
https://stackblitz.com/edit/typescript-eztrai
const date = new Date('2000/01/01');
console.log(`The day is ${date.getDate()}`);
const date1 = new Date('2000-01-01');
console.log(`The day is ${date1.getDate()}`);
And it logs this:
The day is 1
The day is 31
So it seems like using backslashes should work ...
Or perhaps using the year, month (0 based index), and day constructor values like this:
const date3 = new Date(2000, 0, 1);
date3.setHours(0, 0, 0, 0);
console.log(`The day is ${date3.getDate()}`);
console.log(`The date string is ${date3.toDateString()}`);
console.log(`The ISO string is ${date3.toISOString()}`);
console.log(`Get month ${date3.getMonth()} `);
console.log(`Get year ${date3.getFullYear()} `);
console.log(`Get day ${date3.getDate()} `);
NOTE
Runar mentioned something really important in the accepted answer comments. To get consistent results when using the Javascript Date API use methods like getUTCDate(). Which will give us 1 if the date string is 2000-01-01. The getDate() method could give us a different number ...
From the ECMA standard of the Date.parse method:
When the UTC offset representation is absent, date-only forms are interpreted as a UTC time and date-time forms are interpreted as a local time.
What is happening is that New Date() implicitly calls Date.parse on the string. The "2000-01-01" version conforms to a Date Time String Format with a missing offset representation, so it is assumed you mean UTC.
When you use "2000/01/01" as input the standard has this to say:
If the String does not conform to that format the function may fall back to any implementation-specific heuristics or implementation-specific date formats.
So in short the browser can do what they want. And in your case it assumes you mean the offset of the local time, so whichever offset you are located in gets added when you convert to UTC.
For consistent results, perhaps you want to take a look at Date.UTC
new Date(Date.UTC(2000, 0, 1))
If you need to pass in an ISO string make sure you include the time offset of +00:00 (is often abbreviated with z)
new Date("2000-01-01T00:00:00Z");
If you want to later set the date to something different, use an equivalent UTC setter method (e.g. setUTCHours).
When you retrieve the date, also make sure to use the UTC getter methods (e.g. getUTCMonth).
const date = new Date("2000-01-01T00:00:00Z");
console.log(date.getUTCDate());
console.log(date.getUTCMonth());
console.log(date.getUTCFullYear());
If you want to retrieve the date in a specific format you can take a look at Intl.DatTimeFormat, just remember to pass in timeZone: "UTC" to the options.
const date = new Date("2000-01-01T00:00:00Z");
const dateTimeFormat =
new Intl.DateTimeFormat("en-GB", { timeZone: "UTC" });
console.log(dateTimeFormat.format(date));
I'm currently just practising JavaScript and I'm trying to create a programme that calculates how many days there are until your next birthday.
I have seen on this site that there is a daysBetween function that I can use to tell the time difference between two dates (I just need to turn these dates into the millisecond value since the 1st Jan 1970).
The problem is that, although one of those dates is the current date (which is easy to convert into its millisecond value), the second is derived from answers the user inputs as a string into a prompt command (there are three different boxes that ask for the year, month and date of their birth). Is there a way I can convert these input strings into a date format that I can then use to find the days between today's date and their next birthday?
Thanks and sorry if this is a stupid question!
Remember in JS that months are indexed from 0, so January === 0.
var date = new Date('2017','5','25'); would be today, assume you have something like:
var userDd = '25';
var userMm = '6'; // User doesn't know the months are indexed at 0.
var userYy = '2017';
var date = new Date(userYy, userMm - 1, userYy);
date.getTime(); // returns the milliseconds value.
I have tried to search for the answer already, and although I find answers that are very similar, I don't think they are exactly what I am looking for. Please forgive me if this is already answered elsewhere.
I am trying to parse an ISO date in javascript so that I can compare it to the client system date and display information depending on if the ISO date is before or after the client system date.
This was fine until I needed to support IE8 and now I am stuck.
I have created a function because I have three different dates that I need to do this to.
for example, my ISO date is: 2015-12-22T11:59 in UTC time.
but once my date is parsed, the full date is 11:59 in local time, no matter which time zone i test, it's always 11.59 in THAT time zone.
I know that the function I have created currently doesn't do anything with timezone, this is where I am stuck. I don't know what to add to get my end date to change as a reflection of the timezone of the clients machine.
any help or advice would be greatly appreciated.
I am not able to use something like moments.js because I have an upload restriction.
Jquery is available though. or plain javascript.
<script>
function setSaleContent() {
//creating a new date object that takes the clients current system time. so we can compare it to the dates stored in our array
var currentDate = new Date();
console.log(currentDate + " this is the clients date ");
//These variables actually come from an external array object, but I'm putting them in here like this for this example.
var destinations = {
freedate: "2015-12-16T11:59",
courierdate: "2015-12-22T11:59",
nextdaydate: "2015-12-23T11:59",
}
//fetch all the ISO dates from the array.
var freeDateISO = destinations["freedate"];
var courierDateISO = destinations["courierdate"];
var nextdayDateISO = destinations["nextdaydate"];
//I am creating this reusable function to split up my ISO date for the sake of IE8.. and create it into a date format that can be compared against another date. I know that this isn't doing anything with my timezone and that is where my problem lies.
function parseDate(str) {
var parts = /^(\d{4}).(\d{2}).(\d{2}).(\d{2}):(\d{2})/.exec(str);
if (parts) {
return new Date(parts[1], parts[2] - 1, parts[3], parts[4], parts[5]);
}
return new Date();
}
//I would like this date to change to reflect the time zone of the clients system time.
//currently returns the date at 11.59 regardless of timezone.
//If i was in GMT i would want it to say 11.59
//If i was in CT time I would like this to say 05.59
//If i was in Perth I would like this to say 19:59
var freeDate = parseDate(freeDateISO);
console.log(freeDate + " this is the converted date for IE")
}
window.onload = setSaleContent;
The simple solution is to append Z to the ISO date to indicate it is in UTC time, such as 2015-12-22T11:59Z.
When JavaScript parses that date as a string, it will then automatically convert the UTC date to the local time zone.
While this is simple enough with a parsing call in the form new Date(str);, it will not play nice with your parse call with numerical arguments targeting IE8 and other old browsers.
A polyfill for parsing ISO dates with timezone exists: Javascript JSON Date parse in IE7/IE8 returns NaN
This can replace your custom parseDate function after some modification to take an input string.
Alternatively, implement your own custom date manipulater to account for the local timezone using the .getTimezoneOffset() method on the newly created date, which gives the time zone offset in minutes, but you will have to come up with a method of utilising the offset such as adjusting hours and minutes, due to the limited methods of the JavaScript date object.
I have a date string that looks like this: 2014-07-21T12:55:31.513Z. Is there some simple way to convert this to a date? I found that there is Date.parse() however that dives me milliseconds since Jan. 1st, 1970 which it doesn't look like that fits my needs.
new Date("2014-07-21T12:55:31.513Z")
You should also have a look here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date
use
new Date('2014-07-21T12:55:31.513Z')
the ISO format:
YYYY-MM-DD
or
YYYY-MM-DDTHH:MM:SS
refer Date
Note: Where Date is called as a constructor with more than one
argument, if values are greater than their logical range (e.g. 13 is
provided as the month value or 70 for the minute value), the adjacent
value will be adjusted. E.g. new Date(2013,13,1) is equivalent to new
Date(2014,1,1), both create a date for 2014-02-01 (note that the month
is 0-based). Similarly for other values: new Date(2013,2,1,0,70) is
equivalent to new Date(2013,2,1,1,10) which both create a date for
2013-03-01T01:10:00.
Not sure if this is the best way but I would just parse the string to isolate the year, month, day, hours, minutes, seconds and milliseconds the use the following function:
var date = new Date(year, month, day, hours, minutes, seconds, milliseconds);
I'm using moment.js 1.7.0 to try and compare today's date with another date but the diff function is saying they are 1 day apart for some reason.
code:
var releaseDate = moment("2012-09-25");
var now = moment(); //Today is 2012-09-25, same as releaseDate
console.log("RELEASE: " + releaseDate.format("YYYY-MM-DD"));
console.log("NOW: " + now.format("YYYY-MM-DD"));
console.log("DIFF: " + now.diff(releaseDate, 'days'));
console:
RELEASE: 2012-09-25
NOW: 2012-09-25
DIFF: 1
Ideas?
Based on the documentation (and brief testing), moment.js creates wrappers around date objects. The statement:
var now = moment();
creates a "moment" object that at its heart has a new Date object created as if by new Date(), so hours, minutes and seconds will be set to the current time.
The statement:
var releaseDate = moment("2012-09-25");
creates a moment object that at its heart has a new Date object created as if by new Date(2012, 8, 25) where the hours, minutes and seconds will all be set to zero for the local time zone.
moment.diff returns a value based on a the rounded difference in ms between the two dates. To see the full value, pass true as the third parameter:
now.diff(releaseDate, 'days', true)
------------------------------^
So it will depend on the time of day when the code is run and the local time zone whether now.diff(releaseDate, 'days') is zero or one, even when run on the same local date.
If you want to compare just dates, then use:
var now = moment().startOf('day');
which will set the time to 00:00:00 in the local time zone.
RobG's answer is correct for the question, so this answer is just for those searching how to compare dates in momentjs.
I attempted to use startOf('day') like mentioned above:
var compare = moment(dateA).startOf('day') === moment(dateB).startOf('day');
This did not work for me.
I had to use isSame:
var compare = moment(dateA).isSame(dateB, 'day');