There is limited guidance for CosmosDB stored procedures and their handling of new Date() and the comparison of dates.
The following code is a CosmosDB stored procedure to 'freeze' the writing of documents after a given time. The property currentDoc.FreezeDate is in ISO-8601 format, e.g. '2017-11-15T13:34:04Z'.
Note: this is an example of the situation I'm trying to understand. It is not production code.
function tryUpdate(newDoc) {
__.queryDocuments(
__.getSelfLink(),
{ /* query to fetch the document */ },
(error, results) => {
var currentDoc = results[0]; // doc from the database
// fail if the document is still locked
if (new Date(currentDoc.FreezeDate) < new Date()) {
getContext().getResponse().setBody({ success: false });
return;
}
// else update the document
/* snip */
}
);
}
My question is: within CosmosDB stored procedures, is new Date() affected by timezones, especially given that the database may be in a different region than the invoking code? Is the date comparison code here valid in all situations?
As far as I can see, CosmosDB is storing DateTime values without the corresponding Timezone, aka. not as DateTimeOffset. This means it should not matter where the code is executed, since it is always normalized to something like this:
"2014-09-15T23:14:25.7251173Z"
Javascript Date object are timestamps - they merely contain a number of milliseconds since the epoch. There is no timezone info in a Date object. Which calendar date (day, minutes, seconds) this timestamp represents is a matter of the interpretation (one of to...String methods).
(taken from Parse date without timezone javascript)
In other words, no matter where you are in the world, new Date() will always have the same value internally.
If you want to remove uncertainty in exchange for readability, I would recommend only storing the seconds or milliseconds since the epoch (Unix Time). This is also what is used internally by date (new Date().value - milliseconds). Incidentally, the internal cosmos document field _ts is also a timestamp in epoch format.
Be aware that the value of new Date() might by off the 'correct global time` by a couple of minutes - I don't know if Azure/Cosmos guarantees a certain deviation window.
Related
I recently tried to assign a new date in MongoDB, but I have a problem with that, it stored the date I give but it's not correct
userSchema.methods.createPasswordResetToken = async function () {
this.passwordResetToken = crypto.randomBytes(20).toString('hex')
this.passwordResetExpires = moment().format(this.createAt)
await this.save()
console.log(moment().format(this.createAt)) // 2021-12-21T19:01:54+02:00
console.log(this.passwordResetExpires) // 2021-12-21T17:01:54.000Z
return { token: this.passwordResetToken, userId: this._id }
}
mongoDb remove 2 hours when storing it
and when I try to catch the type of two values
I got
console.log(moment().format(this.createAt)) // string
console.log(this.passwordResetExpires) // object
:
user Schema
...
passwordResetToken: String,
passwordResetExpires: Date
...
From the docs:
MongoDB stores times in UTC by default, and will convert any local time representations into this form. Applications that must operate or report on some unmodified local time value may store the time zone alongside the UTC timestamp, and compute the original local time in their application logic.
It seems your server just sits in GMT timezone ( utc +2, you could also see it from your date value // 2021-12-21T19:01:54+02:00 ). I would usually offer some hacky way to get around the issue but this is actually a best practice. Hence I recommend you do your date calculations in UTC and not in machine time.
note your other date is in UTC (2021-12-21T17:01:54.000Z), make sure your comparing apples to apples.
Consider the code :
let now = moment();
console.log(now.format()); // 2019-11-25T20:23:50+02:00
console.log(now.toDate()); // 2019-11-25T18:23:50.916Z
This is the output on my local machine , and when I check the app on Heroku
it gives the same values , even though I changed the TZ like this :
heroku config:add TZ="Asia/Jerusalem"
How can I get a JavaScript Date (Not a String !) object of my localtime , meaning 2019-11-25T20:23:50 ?
Let's walk through your code example:
let now = moment();
You create a Moment object. You don't pass any parameters, so it is initialized using the current timestamp (as if you called Date.now()) and set to "local mode".
console.log(now.format()); // 2019-11-25T20:23:50+02:00
By calling format, you ask the Moment object to produce a String. Since it's in local mode, the offset that applies to that moment in time for the local time zone is emitted in the result, and the wall time shown in the result is adjusted for that offset. In this case, the local time is two hours ahead of UTC. You then pass that string to console.log, which emits it to the console.
console.log(now.toDate()); // 2019-11-25T18:23:50.916Z
By calling toDate, you ask the Moment object to create a Date object. The "mode" of the moment object is no longer relevant because Date objects don't track anything other than a timestamp. Thus, the timestamp within the Moment object becomes the timestamp for the resulting Date object. Since you derived the Moment object from the current time, the result is the same as if you just called new Date() to begin with.
You then pass the string to console.log - except one can't just log an object, so it first has to convert it to something so you can see it. Here's the interesting part: There is no spec for this behavior. Implementations of ECMAScript can do whatever they like in this regard. Some implementations, like in your example, will call .toISOString() and log the result. Since .toISOString() displays the result in UTC, the result of logging a Date object is also shown in UTC. But other implementations will call .toString() on the Date object and log that, the result being in local time. It's entirely possible some future implementation could show the result in some graphical or interactive output. The point being, you can't rely on the behavior of console.log(Date) to be consistent.
No amount of changing your time zone settings will change this result. The Date object is inherently UTC-based, your output is also UTC-based, and UTC is the same over the whole planet (by design).
If you want the time zone reflected in the string output, you must use a function that produces a string with respect to local time. As you showed, you'll get that with .format() on a Moment object in local mode. You can also get one from calling .toString() on a Date object (but the resulting string is not in the same ISO 8601 format).
i would try,
moment().local().toDate()
but if you are planning to save date into db it's good practice to save time in UTC format for easier global conversion.
If you want to work timezones you may require also moment timezone package - https://momentjs.com/timezone/docs/
npm install moment-timezone
Hope this helps :)
I have a table in my psql database with a "trigger_time" column of type "TIMESTAMP WITH TIME ZONE DEFAULT now()"
I data in the row is this 2018-06-27 15:45:00-03.
When running from psql console
SELECT trigger_time AT TIME ZONE 'UTC'
FROM tasks
WHERE task_id = 1;
this query returns "2018-06-27 18:45:00".
Similarly when I run
SELECT trigger_time AT TIME ZONE 'America/Glace_Bay'
FROM tasks
WHERE task_id = 1;
I get 2018-06-27 15:45:00
Using knex.raw("SELECT trigger_time AT TIME ZONE 'America/Glace_Bay' FROM tasks WHERE task_id = 1") I get 2018-06-27T18:45:00.000Z and when running knex.raw("SELECT trigger_time AT TIME ZONE 'UTC' FROM tasks WHERE task_id = 1") I get 2018-06-27T21:45:00.000Z
Both of these results from knex are incorrect, how do I get knex to stop silently altering my data?
Probably things are failing because when you are querying datetimes from database in certain timezone and effectively converting type of timestamp to be timestamp without timezone. In that case database will not send information to knex about in which timezone that returned time was.
So knex (or rather pg driver which knex is using) interprets your timestamp as local time, which depends of timezone setup of your application server running knex.
You could fetch time just as UTC and do timezone conversion in JavaScript side with moment or luxon libraries (IMO latter is better for timezone handling).
Other solution would be to tell pg driver that timestamp and timestamp with timezone types should not be converted to JavaScript Date objects.
It can be done like this (https://github.com/brianc/node-pg-types):
const types = require('pg').types;
const TIMESTAMPTZ_OID = 1184;
const TIMESTAMP_OID = 1114;
types.setTypeParser(TIMESTAMPTZ_OID, val => val);
types.setTypeParser(TIMESTAMP_OID, val => val);
This code which makes all timestamps to be returned as strings may be added to for example in start of knexfile.js. Those returned strings will be exactly in the same format that they were returned by database server itself.
EDIT:
In code in the original post, when timestamp is converted to be in time zone UTC database server converts timestamp with time zone type to be normal timestamp without time zone so returned value doesn't have timezone information. To add timezone information back you can for example append +02 to the end of returned time stamp like this:
select ('2010-01-01T00:00:00.000Z'::timestamptz AT TIME ZONE 'UTC')::text || '+00';
Which returns 2010-01-01 00:00:00+00 to the driver which can be read correctly by pg driver too.
This will effectively do the same thing that just setting SET TIME ZONE 'UTC'; in db server when connection is created and just returning timestamptz column directly:
SET TIME ZONE 'UTC';
select '2010-01-01T00:00:00.000+02:00'::timestamptz;
Which will return 2009-12-31 22:00:00+00.
I have a moment.js object whose Unix epoch value I'd like to change.
Normally I'd use myMoment = moment(someEpoch);, but because of design constraints I'm having to pass the object by reference, so I must mutate the value rather than replacing it altogether.
What is the neatest and (ideally) most performant way to do this in v2.15+?
Assuming m is a moment object, and t is the timestamp to set (in ms), probably the easiest way is:
m.add(t-m);
Or if you prefer to be more verbose:
m.add(t - m.valueOf(), 'ms');
Note that the default units are milliseconds when not specified and the input is numeric. If your input timestamp is in whole seconds, you'd have to multiply it by 1000 in either of the above formulas before subtracting the value of m.
However, if you're really after the most efficient code in terms of minimizing total operations performed internally, you could modify moment internals directly. Doing so is dangerous in that there's no guarantee the internals won't change between versions. Only the public API compatibility is guaranteed, following SemVer rules. So only do this if you are optimizing for perf and are willing to deal with potentially breaking changes in the future:
m._d.setTime(t + ((m._offset || 0) * 60000));
This is essentially an inversion of moment's valueOf function, and is probably what the implementation would look like if it were built in to moment.
Of course, if you are only working with moments in UTC mode, you can just do:
m._d.setTime(t);
One last thing, with regard to terminology, you can't actually set "the Unix epoch value", because the epoch is a fixed value. In this context, "epoch" means the timestamp that is zero, which is associated with 1970-01-01T00:00:00.000Z. It cannot be changed. You are simply using a "Unix Timestamp in milliseconds", or perhaps an "epoch-based timestamp". But it is a misnomer for your variable to be named someEpoch.
moment.js has a method to do that:
moment.unix(Number)
http://momentjs.com/docs/#/parsing/unix-timestamp/
I have a date-filter component that I am using in my Ember application that only works on initial render, not on a page reload, or even if I save a file (which triggers the application to live update).
In the main template of my application, I render the date-filter like this passing it a unix timestamp
{{date-filter unixepoch=item.date}}
Then, in components/date-filter.js, I use a computed property called timeConverter to change the unix epoch into a time string formatted according to user's language of choice, and then in my templates/components/date-filter.hbs file I do {{timeConverter}} to display the results
timeConverter: function(){
//step 1: get the epoch I passed in to the component
var epoch = this.get('unixepoch');
//step 2: create a human readable date string such as `Jun 29, 2015, 12:36PM`
var datestring = new Date(epoch)
//do language formatting --code omitted as the problem is with step2
}
It is step 2 that fails (returning invalid date) if I refresh the page or even save the file. It always returns the proper date string the first time this component is called. Even if I do new Date(epoch) in the parent component, and try to pass the result in to this component (to do foreign language formatting), I'm having the same problem.
Question: how can I figure out what's happening inside new Date(epoch), or whether it's an issue related to the component?
I suspect your epoch value is a string (of all digits). If so, then
var datestring = new Date(+epoch);
// Note ------------------^
...will fix it by converting it to a number (+ is just one way to do it, this answer lists your options and their pros/cons). Note that JavaScript uses the newer "milliseconds since The Epoch" rather than the older (original) "seconds since The Epoch." So if doing this starts giving you dates, but they're much further back in time than you were expecting, you might want epoch * 1000 to convert seconds to milliseconds.
If it's a string that isn't all digits, it's not an epoch value at all. The only string value that the specification requires new Date to understand is the one described in the spec here (although all major JavaScript engines also understand the undocumented format using / [not -] in U.S. date order [regardless of locale]: mm/dd/yyyy — don't use it, use the standard one).