I'm trying to compare dates from database (firebase) with NOW. I'm using moment.js and it's not working. I think it has something to do with the time zone (or UTC+01:00)...
Example.
date1: "2016-11-20T14:00:00"
NOW: "2016-11-20T14:49:20+01:00"
I get NOW with moment() and compare like this:
var date1 = moment("2016-11-20T14:00:00");
moment(date1).isSameOrAfter( moment() ) // returns true
The comparison is precisely one hour off... How can I fix this? AND: is there any best practice in storing and comparing dates across time zones.
Dates should always be saved in UTC. If you use string type the UTC date time value in ISO format.
So while saving convert from client time zone into UTC and while retrieving convert from UTC into client time zone.
Comparison should be done between two dates in the same time zone.
If the database value is in UTC and then you have to parse as .utc() while creating a moment object.
moment.utc("2016-11-20T14:00:00");
Change the NOW value to UTC before comparing.
moment.(date1).utc()
Alternatively you can change the database value from UTC to local.
moment.utc("2016-11-20T14:00:00").local()
Keep the NOW value as is before comparing.
You cannot compare the date you stored in Firebase with now() as it lacks the information about your timezone.
You can store dates using Firebase.ServerValue.TIMESTAMP
For Example:
date1: Firebase.ServerValue.TIMESTAMP
This will save your time in Unix Milliseconds (time since the Unix epoch, in milliseconds) by the Firebase Database servers.
Then you can compare with new Date().getTime() this will give your device time in Unix Milliseconds.
For Example:
if(new Date().getTime() >= date1) {
//do something
}
Hope it helps :)
Related
I am processing some itinerary data where the times and dates are all provided in the local timezone. I am adding this data to a database where I'd like to store all of the dates in UTC, with the proper timezone offset. I'm trying to process these dates with moment.js.
The input string for date/time is formatted like this 2020-07-12 13:00 and the timezone is in this format Europe/Amsterdam.
I want to end up with a string like:
2020-07-12T11:00:00+02:00
The trouble I'm having, is that moment converts my input time to either local time or utc if I use the .utc() method.
This code is getting me the correct result, but I don't understand why and I'm not sure if I can rely on its accuracy:
var offset = moment.tz(`Europe/Amsterdam`).utcOffset();
var m = moment(`2020-07-12 13:00`, 'YYYY-MM-DD HH:mm').utc().subtract(240 + offset + offset, 'minutes').utcOffset(offset); // (240 is my own UTC offset)
How can I simply input a date, time and timezone and end up with a correct ISO8601 DateTime?
If you are already using Moment and Moment-TimeZone in your app, then you can simply do the following:
const m = moment.tz('2020-07-12 13:00', 'YYYY-MM-DD HH:mm', 'Europe/Amsterdam');
m.format() //=> "2020-07-12T13:00:00+02:00"
However, the Moment team recommends using Luxon for new development. The equivalent is:
const dt = luxon.DateTime.fromFormat('2020-07-12 13:00', 'yyyy-MM-dd HH:mm', { zone: 'Europe/Amsterdam'});
dt.toISO() //=> "2020-07-12T13:00:00.000+02:00"
The only difference being that milliseconds are included. You can use a different formatting function if you prefer a different output.
The main benefit of Luxon is that it uses the built-in time zone functionality provided by the ECMAScript Internationalization API, whereas Moment-Timezone bundles its own time zone data - which can be quite large.
Also, note that in your question by asking for 2020-07-12T11:00:00+02:00 you seem to be misunderstanding the ISO 8601 format. In that format, the time presented is the local time. Thus, it should be 13:00, not 11:00. The +02:00 means, "this was the offset from UTC for this local time". (It doesn't mean that you apply the offset to get the local time.)
I am receiving a timestamp from a third-party API, that looks like: 1540388730994. However, I have been informed that this timestamp is in 'Europe/Amsterdam' timezone.
I need to convert this timestamp to UTC, as we store all our dates in UTC.
How is this possible in JavaScript?
So far I have tried:
const timestamp = 1540388730994
const timestampInUTC = moment.tz(timestamp, 'Europe/Amsterdam').utc().valueOf()
console.log(timestamp, timestampInUTC)
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.22.2/moment.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment-timezone/0.5.21/moment-timezone-with-data-2012-2022.min.js"></script>
However, you can clearly see that the two output timestamps are identical, whereas I would have expected the conversion to subtract 1-2 hours, as Amsterdam timezone is GMT+2.
What am I doing wrong here?
Timestamps in numeric form are always in UTC. If they've for some reason manually added/subtracted it by a time zone offset, they are doing it wrong. You don't see any change from moment, because a UTC timestamp is the same moment in time regardless of what time zone you represent the local time equivalent in. If you expected the timestamp to change, that would be representing an entirely different moment in time.
I want to construct a Date object along with dynamically selected timezone. I am currently in IST time zone. I want to eliminate the usage of Date.parse() as it does not behave as expected at times.
let's assume tzOffset to be +05:30 for now. It could be any other timezone based on what users want. new Date(epochDate).toISOString(); converts the date to UTC timezone. How do I get the date in toISOString() format but also get it in the desired time zone
const tsConstruct = `${year}-${month}-${date}T${hour}:${min}:00${tzOffset}`;
const epochDate = Date.parse(tsConstruct);
scheduledTs = new Date(epochDate).toISOString();
JavaScript's Date does not store timezone info. It just stores the number of milliseconds from UNIX EPOCH. Then, depending if you use the UTC methods or not, it returns the date and time in UTC or the local time.
You should have to change the date and time, based on the timezone indicated, to UTC or local time, and then store it in a Date object. But, of course, to show the stored time in another timezone different to the local one or UTC, you must do the conversions yourself, so, as #RuChengChong suggested, use a helper library like momentjs.
I am having trouble when converting from time zone to time zone using moment.js.
This is my code:
convertSelectedTimeZoneToClients() {
let timeZoneInfo = {
usersTimeZone: this.$rootScope.mtz.tz.guess(),
utcOffset: this.formData.timeZone.offset,
selectedDateTime: this.toJSONLocal(this.formData.sessionDate) + " " + this.formData.sessionTime
};
let utcTime = this.$rootScope.mtz.utc(timeZoneInfo.selectedDateTime).utcOffset(timeZoneInfo.utcOffset).format("YYYY-MM-DD HH:mm");
let con = this.$rootScope.mtz.tz(utcTime, timeZoneInfo.usersTimeZone).format();
return con;
}
The user picks date, time and time zone from drop downs on client page.
In timeZoneInfo object I am storing usersTimeZone (I want to be able to convert timezone that user selected on page and convert it to his local time zone).
For example user picks: 11/08/2016 01:30 and UTC+2 timezone and his timezone is UTC+1, than I want to show him in label: That is 11/08/2016 00:30 since UTC+1 is -1 hour comparing to UTC+2 timezone.
I store offsets for time zones in one object and those values are hard coded (utcOffset: this.formData.timeZone.offset).
Before I convert time form time zone to time zone I do this: get time zone -> convert to UTC time -> convert to user time zone.
What is happening is that utcTime variable has correct value. But when I pass that value and users time zone to .tz() function and using format() to get some readable value I get same time as utcTime like shown in picture:
I have read moment.js docs and by them this .tz().format() should do the work, but as you can see my result is: 2016-11-08T23:30:00+01:00.
So it gets that is should be incremented by 1 hour but how to accomplish to get: 2016-11-09T00:30 instead?
I have tried .format("YYYY-MM-DD HH:mm") as well same problem. When I use .local() function that should convert from utc time to specified time zone same problem is present.
Am I getting something wrongly? I am pretty sure that when you convert from 2016-11-08T23:30 UTC to UTC+1 it should be 2016-11-09T00:30, or one hour forward. Does someone sees something strange in this code?
I am calling an API that returns a date/time string such as "2014-04-30 15:32:01". On top of this, I have a known timezone that this date/time exists in. I can see from the javascript Date() class has a .UTC() call for this, but that does not seem to accept a timezone as far as I can tell.
Given the date/time string + timezone, how can I convert those into a UTC timestamp?
I'd recommend using Moment.js and Moment Timezone.
You can create a timestamp using Date.parse from your local time (RFC2822 date format to include the timezone), create a date from that and use Date.toUTCString to get the UTC time. Not sure if it'll work with day light savings though.
Example: http://jsfiddle.net/3vXV6/ (will alert the date)
References:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/parse
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toUTCString