I am trying to convert UTC time to Local Timezone. I only require the date to be extracted. When I try the below it works and gives correct results.
select to_date(FROM_UTC_TIMESTAMP(current_timestamp(), 'Pacific/Fiji'));
But if I try, short ID of the respective timezone it is giving wrong results.
select to_date(FROM_UTC_TIMESTAMP(current_timestamp(), 'FJT'));
The issue was with the difference in GMT and UTC short IDs. In the above example 'Pacific/Fiji' is a UTC based short ID where are 'FJT' is GMT equivalent. Since we are using hive function FROM_UTC_TIMESTAMP we have to use UTC based short IDs. Here is a list of UTC based short IDs
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I am building a flutter/firebase chat app and storing timestamps of messages in UTC. I am using this line of code to convert local time to UTC. 'time': DateTime.now().toUtc().toString(), When I tested this with two users one is in Virginia, US, and the other one in Sri Lanka. The timestamp of the user in Sri Lanka is converted correctly to UTC, but for user in Virginia time is correct but the date as of yesterday.
Sri Lanka Time: 2020-06-21 20:50:48
UTC converted: 2020-06-21 15:20:48.027446Z
Virginia Time: 2020-06-21 11:24:38
UTC converted: 2020-06-20 15:24:38.594194Z
My whole app malfunctioned because of this and order of messages got weird. How to solve this issue?
If you are using Firebase-Realtime database then use this code
timeStamp = ServerValue.timestamp;
If you using Firestore then use this code
timeStamp = FieldValue.serverTimestamp();
You don't need to store the timestamp by yourself. Firestore offers timestamp. See https://pub.dev/documentation/cloud_firestore/latest/cloud_firestore/FieldValue/serverTimestamp.html
I will begin using MongoDB in a project and made the following observation:
A ‘Date’, e.g.: ISODate("2000-07-24T00:00:00.000Z") is stored in as UTC 0 (or Zulu).
Let’s assume that an end user submits a plain date, such as “2000-07-24” and his or her local timezone is -5.
Because of the ‘Z’ character in the time (indicates UTC 0), storing the following would be incorrect because the user’s 5 hour difference:
ISODate("2000-07-24T00:00:00.000Z")
I am assuming that it would be more proper to consider the end user’s local time zone into account and store the date as follows:
ISODate(“2000-07-23T19:00:00.000Z”)
By doing this, I can see that any queries would need a timezone adjustment for 'Date'.
By storing all ‘Date’ fields as UTC 0, we can guarantee that exact points in time from people posting from different continents is properly handled.
Does this seem like a good way to handle timezones in MongoDB?
How to convert given UTC date time to PST date time, by keeping the daylight stuff in time calculations?
Note that the server I am hitting is in utc. I mean, GETDATE() = GETUTCDATE().
Also, we can't use AT TIME ZONE, as DB is on older SQL Server.
Thanks in advance for the help.
Search the site, example: Convert Datetime column from UTC to local time in select statement
Read the link above, also include daylight stuff in there for some of the responses too.
My console is PST.
Database server and times stored are GMT.
I'm having to run queries like so:
SELECT x,y,z
FROM tbl_msg
WHERE (msg_datetime AT TIME ZONE 'BST') BETWEEN '2016-11-21'::date and '2016-11-22'::date;
Indexing 101 says that performing this operation on msg_datetime will now avoid the index and this is what I'm seeing.
So I need advice with an indexing solution for this.
Can I index this timezone? or alter this query so that it queries these times in BST, converted to GMT?
You should have msg_datetime column of type timestamp with time zone (or shorter alias timestamptz) with normal index.
Then, to get data for these 2 days, you should:
set timezone 'Europe/London'; -- once, on connection start
SELECT x,y,z
FROM tbl_msg
WHERE
msg_datetime>='2016-11-21 00:00:00'
and
msg_datetime<'2016-11-23 00:00:00';
You should not use ordinary timestamp, as it stores literal date and hour without information about which timezone it actually meant. A timestamp with time zone type will automatically convert your client's configured time to internal representation (which is in UTC) and back. You can also express timestamptz from non-default timezone using for example '2016-11-23 00:00:00 Asia/Tokyo'.
Also you should not use BST - because you'd need to use GMT on winter and remember when to use which. You should use 'Europe/London' or other "city" timezones (list), which are right both in summer and in winter.
I have various timestamps stored in Mongo collections, some as floats and some as ints.
They are all stored in BST and the server will be switched to UTC soon. How do I convert them within Mongo to be UTC timestamps?
In MySQL I can do this:
UPDATE `table` SET `field` = CONVERT_TZ(`field`, 'Europe/London', 'UTC');
Is there a Mongo equivalent?
You'll have to use your language of choice and update them one at a time. It should be as simple as a for loop that loads the data and rewrites it.
Just double-check how your language of choice handles timestamps across timezones. Making such a data change can have all kinds of unexpected effects on production code.
Timestamps are generally in UTC and not in a specific timezone. All date/time libraries I've worked with return timestamps that are the number of seconds (or milliseconds) since Jan 1st 1970 UTC. Check the documentation for the library you used to create the timestamp to be sure.
This means that you should be ok, unless you have used a date/time library that does not follow this convention, or somehow calculated the timestamps yourself and accounted for the timezone.
For example in JavaScript if you store the value returned from new Date().getTime() and later pass that value to new Date(...) on a different system you will end up with the same absolute date/time, regardless of the timezones of the two systems. The same goes for Ruby, do Time.new.to_i on one machine, and run Time.at(...) on another and you will get the same absolute date/time. When I say "absolute date/time" I mean that it's UTC time will be the same, most likely the system will display it in the local time zone, but that is what you want.
Some points to consider about date in Mongo:
All dates are stored in UTC in MongoDB
MongoDB stores dates internally as a 64 bit integer representing
milliseconds since 1970-01-01T00:00:00Z
If the date value you provide is not already in UTC it
will be converted to UTC before being stored in MongoDB by the driver
The recommendation is not to use DateTime.Parse.
You will get into all sorts timezone issues regarding how DateTimes are formatted.
Instead just use one of the DateTime constructors with UTC flavor.
Example:
var dateTime = new DateTime(2011, 5, 5, 0, 0, 0, DateTimeKind.Utc);
Hope you find it useful.