When I write a Timestamp on Firestore it shows 6.00PM on database though I have not defined any time in the Date object.
My Approach to get Timestamp from date :
let reservationDate = new Date(year,month,dayOfMonth);
let bookedRoomData = {
....
...
reservationDate: admin.firestore.Timestamp.fromDate(reservationDate),
...
};
What is the reason behind showing 6.00PM instead of 12.00AM ?
What should be done to fix this?
Screenshot of database is given bellow -
Since you tagged this google-cloud-functions, I'm assuming that your code is running in Cloud Functions.
When you create a new Date object on any machine, it uses the local machine's sense of timezone. So you're making a date at midnight in whatever timezone has been assigned to your Cloud Functions instance. It's not the timezone where you're computer's clock is set.
When you see a timestamp in the console, it's always going to appear on your computer's clock's configured timezone. So, your computer is 6 hours behind whatever is being used by Cloud Functions.
If you want a specific time, you should make sure your Date is configured that way. Consider using a library such as momentjs to create dates according to timezones of your interest. Bear in mind that Timestamp objects do not encode a timezone. They just render in the console according to your local timezone.
Related
Some events don't take place at any specific time and instead are meant to be valid for the whole day irrespective of the time zone the user is at.
For the sake of argument, let's say a system sitting on a server (up in the cloud) runs a job at 5 am and imports data from a different system between this run and the last (24 hours ago). The actual user sitting at his desk doesn't know when the job runs, the user only knows that they go to sleep at night, the server crunches all the entries for the day.
The next morning the user wants to see all the entries from yesterday (what ever the job produced) and they go to the app, pull up a calendar input selector and they pick the 5/26/2022 (today being 5/27/2022).
Assuming the developers followed best practices, the client will transform the date into it's UTC version and send it up through an API. Chances are, depending on where the user is located and the server is, there might be a mismatch.
I could send the date up without it being UTC or I could send a UTC date and try to adjust it back to local time so that I could then compare with the date on record (that exists without an actual time zone).
What I am asking is:
What's the more conventional answer to this particular problem?
Is the idea of a date without time or time zone just ridiculous?
Use UNIX Time. It will give you a timestamp that is universal no matter what timezone the user is in. You can then convert it into whatever timezone you want to.
The concern you describe is well solved/addressed by the ISO 8601 dates/time presentation protocol.
All modern software can read/write dates in ISO 8601.
In Unix machines, the correct command is date with option -I
-I[FMT], --iso-8601[=FMT]
output date/time in ISO 8601 format. FMT='date' for date
only (the default), 'hours', 'minutes', 'seconds', or 'ns'
for date and time to the indicated precision. Example:
2006-08-14T02:34:56-06:00
I use ZingChart to show data as a chart. In the char, I show the data following a time which I get from the server. ZingChart is set as default to follow client time.
I found we can set time zone in a chart only as integer value. However, some time zone are UTC+10:30, UTC+04:30...
So how can we set time zone to ZingChart showing correct time? And if that day has Daylight Saving Time, how should I correct it.
JSON scripts
Unfortunately it appears that ZingChart only supports whole-hour time zone offsets. Not only does this not account for time zones with fixed fractional-hour offsets, but it also doesn't properly account for time zones that use daylight saving time.
The example in the documentation says:
... For example, to set the timezone to Pacific Time, you would add: "timezone":-8.
This is incorrect, as Pacific time is only at UTC-8 during standard time. When it's in daylight time, it uses UTC-7.
This is a common mistake. See "Time Zone != Offset" in the timezone tag wiki. My recommendation to the ZingChart developers would be:
Anywhere you support timezone:-8 you should also support fractional hour offsets such as timezone:5.5 or timezone:8.75.
You should also support named time zone identifiers such as "America/Los_Angeles". To make them work, you'll need to provide a function that the developer can hook into. Don't try to implement the function directly, as there are several libraries already available for this. For example, a developer might combine ZingChart with moment-timezone by writing something like:
zingchart.fnTZOffset = function(timestamp, timeZone) {
return moment(timestamp).tz(timeZone).utcOffset() / 60;
}
ZingChart would invoke this function when timezone was a string and would apply the resulting offset to the specific data point.
Without support from ZingChart, there's not much you can do to properly support time zones.
One other solution to the Daylight Savings time issue some ZingChart users have mentioned in the past is MomentJS. http://momentjs.com
I've read many a post here re: GWT date handling.
One in particular that struck a cord with me was this one
Sending a date and timezone from GAE server to GWT client
Anyhow, there's a need on a project I'm working on to be able to display days, hours, minute intervals as labels in a grid. My team has adopted an approach where all date/time instances are passed the client from the server in ISO8601 String format. The server time zone is to be respected by the client. The biz use case is that all date/time instances are in "market time", so that any browser that visits the app will see and work with dates in the "market time" timezone which happens to be GMT-05:00 (if Daylight Savings in effect) or GMT-06:00 (if Standard Time in effect).
I have posted some source on Github, here:
https://github.com/fastnsilver/gwt-datehandling-example
Particularly...
https://github.com/fastnsilver/gwt-datehandling-example/blob/master/src/main/java/me/fns/gwt/datehandling/client/util/CSTimeUtil.java
and the GWTTestCase
https://github.com/fastnsilver/gwt-datehandling-example/blob/master/src/test/java/me/fns/gwt/datehandling/client/util/CSTimeUtilTestGwt.java
in the hopes that someone can stare at the utility (and test) we're employing for date handling and help us see what we're not seeing.
EDIT
The basic problem is that CSTimeUtil#hoursInDay(Date) is not being calculated correctly in Production mode for "transition days" This method is used by other methods (like CSTimeUtil#dateToHour(Date) and CSTimeUtil#labelsForDay(Date)).
I have deployed our application with the current implementation of CSTimeUtil and it appears to work, but not quite. I'm really confused by alternate test results when e.g., mvn gwt:test is run in GWT Mode or Production Mode on Windows where the OS timezone is set to various timezones other than U.S. GMT-05:00 or GMT-06:00.
Based on some hints from Andrei and some serious blood, sweat and tears, I figured this out on my own. I have updated the code in Github, so if you're curious please go have a look there.
The basics:
Make sure all Strings are ISO8601 (no millis) compliant when sent from server to client and vice versa
Use DateTimeFormat.getFormat("yyyy-MM-ddTHH:mm:ss.SZZZZ") to format and parse dates
Retreive GMT-prefixed time zone info from java.util.Date in "Market time" using DateTimeFormat(Date, TimeZone), where TimeZone param is set as TimeZone.createTimeZone(TZ_CONSTANTS_INSTANCE.americaChicago()) and time zone String retrieved by TimeZone.getISOTimeZoneString(Date)
Generating days, see generateDay(Date, int) or hours generateHour(Date, int), from a source date had to take into consideration that an increment or decrement coudl trigger a change in time zone offset if occurring on a "transition day".
If you time zone is fixed, why would you use a string to represent date/time? You can send a standard Java Date object to the client. If you want, you can even store all dates and times as Longs and pass Longs only. You also send the GWT's TimeZone Json string for your time zone (once per session). You can find it in the GWT - there is a file with strings for all time zones.
On a client you use DateTimeFormat with many predefined formats to display whatever you need: full date, month and date, date and time, etc. Just remember to create TimeZone object from this Json string and use it in DateTimeFormat.getFormat(...).format(Date, TimeZone).
With this approach you don't have to worry about DST changes (they are encoded in that Json string) and locales. You only pass simple Date or Long objects.
In my Play application I have a model with a created field of type Instant. It's populated using a #PrePersist hook which just sets it to a new Instant(). The default timezone is correctly detected as US/Chicago, and when persisted to mysql it appears in the same timezone (in a datetime field).
However, when the object is read back from the database and the time is displayed, it's shown in UTC rather than local time. I'm currently displaying it using
${org.joda.time.format.DateTimeFormat.forStyle("SS").printTo(out, object.created)}
Being new to Joda and fairly new with JPA, I'm not sure if this is a joda problem, a JPA problem, if I should be using a different Joda type, a different mysql type, or if I'm going about this completely wrong. Can someone point me in the right direction?
According to the API UTC seems to be the reference timezone. You can always change that on the DateTimeFormat itself with the withZone(DateTimeZone) method. The following code outputs the date in America/Chicago which seems to be the right timezone in joda-zime:
${org.joda.time.format.DateTimeFormat.forStyle("SS").withZone(org.joda.time.DateTimeZone.forID("America/Chicago")).printTo(out, object.created)}
Following the user guide you can also set the default timezone for joda with DateTimeZone.setDefault(DateTimeZone.forID("America/Chicago")); but I always thought that specifing the default timezone with an VM argument works too and should be the better option.
I'm using GWT on the client (browser) and Joda Time on the server. I'd like to perform some DB lookups bounded by the day (i.e. 00:00:00 until 23:59:59) that a request comes in, with the time boundaries based on the user's (i.e. browser) timezone.
So I have the GWT code do a new java.util.Date() to get the time of the request, and send that to the server. Then I use Joda Time like so:
new DateTime(clientDate).toDateMidnight().toDateTime()
The trouble of course is that toDateMidnight(), in the absence of a specified TimeZone, will use the system's (i.e. the server's) TimeZone. I've been trying to find a simple way to pass the TimeZone from the browser to the server without much luck. In GWT I can get the GMT offset with:
DateTimeFormat.getFormat("Z").fmt(new Date())
which results in something like "-0400". But Joda Time's DateTimeZone.forID() wants strings formatted like "America/New_York", or an integer argument of hours and minutes. Of course I can parse "-0400" into -4 hours and 0 minutes, but I'm wondering if there is not a more straightforward way of doing this.
You could use java.util.Date's getTimezoneOffset() method. It's deprecated, but that's pretty usual for Date handling in GWT currently.
And AFAIR, you can specify something similar to "UTC+4" in Joda time.
Update: I looked it up, and it's "+04:00". Or use DateTimeZone.forOffsetHours() or even forOffsetMillis().
Gwittir (http://www.gwtsite.com) is a library for GWT that includes many cool utilities, like databinding, animation, reflection, and more. However, there are some other interesting goodies as well like the new Joda Time integration. If you have ever been frustrated by GWT’s lack of java.util.Calendar support, you’ll love this, as it makes it easy to do date manipulations in your applications.
otherwise, there are other ways to get timezone offset with + & -.
import java.util.TimeZone;
use: TimeZone.getDefault().getRawOffset()
this function will return the offset time in millisecond about your phone seeting. For Example, GMT-04:00 is equals to (-4)*60*60*1000 = -14400000.
After some operations to get the number which you want.
I have a similar but slightly different problem I think.
I actually need to store the clients timezone on the server, so that I can send out messages about dates stored in their calendar.
The dates are stored in UTC time in google app engine and of course I can store the current Timezone offset when creating the appointment. The problem comes when for instance I want to send out a summary email with a list of upcoming appointments in it. These appointments need to be offset with the correct Timezone adjustments for the client (Im happy to assume that they are still in the same timezone as when they created the appointment).
The real problem comes with Daylight Savings adjustments, so for instance I might have appointments stored for Saturday 30th October 2010 at 1pm (BST[GMT+60]) and Monday 1st November 2010 at 1pm (GMT).
So as you can imagine, I cant just use the current timezone offset (BST) as that would mean that the appointment on Monday 1st November would be listed as 2pm rather than 1pm (GMT+60)
It occurs to me that the best way to deal with this is just to store the timezone offset with each appointment individually, but I feel it would be much better to be able to determine the original timezone correctly in the first place, then just let java do the correct adjustments.