I am running mongodb on ubuntu server. The server time is
root# date
Thu Sep 13 21:15:58 BST 2012
But when I run the following command I get a different result
root# mongo
MongoDB shell version: 2.2.0
connecting to: test
> new Date()
ISODate("2012-09-13T20:15:58.670Z")
There is exactly one hour difference. When I update a documents updated_on field with php using MongoDate(), the value of the field is still 1 hour off.
[EDIT]
Actually I just checked my php error log and the time in the log file is 1 hour off as well
[13-Sep-2012 20:11:14 UTC] Log Message (Time should be 21:11:14)
Mongo tells you
2012-09-13T20:15:58.670Z
Z = Zulu time / Zero offset / UTC. You can also express the time in that TZ as 2012-09-13T20:15:58.670+00:00, as defined in the ISO8601 standard by the way.
BST is UTC+1. So, they are the same time but in different time zones.
You can resolve this issue by displaying the DateTime with ToLocalTime method.
MVC C# Example: #Model.StartDate.ToLocalTime()
This is due to the way MongoDB store datetime in BST format. So the daylight savings time or the time zone of the server will have an effect on the actual date time returned to the application. This simple code will be able to format as usual with ToString("dd MMMM yyyy hh:mm tt") or any other format based on your requirements.
Here you need to understand a concept in time setting in clocks called daylight saving time. In some countries around the world the clock is advanced by 1 or more hours to experience day light by one more hour. The difference between IST and GST is 5.30 hrs but the actual time difference is between New Delhi and London time is 6.30 hrs. See this article from 4GuysFromRolla for setting and using server time.
On windows change your timezone.
Controll Panel -> Date and Time -> Change on timezone -> (UTC) Coordinated universal time.
And then just change your time
Related
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.
Im using this repo
https://github.com/remirobert/Tempo
Can someone help me understand how to grab the current time zone of the device, and then notify tempo? I am using the timeAgoNow() function of tempo to find display how long ago the post was made, but the timezone difference is messing it up. My datasource is using UTC time.
Cocoa uses UTC internally. for all of its date/time calculations.
If you create an NSDate for now:
NSDate()
You get a date that is the number of elapsed seconds since midnight, 1970 in UTC time.
Dates only have time zones when you display them.
By default logging a date to the console logs it in UTC, which can be confusing.
If I'm working on a project that does a lot of date/time calculations I'll create a debugging method that converts an NSDate to a date/time string in the current locale, which is easier to read/debug without having to mentally convert from UTC back to local time.
I have never used Tempo, so I don't know if it is using date strings, NSDate, or "internet dates" (which are also in UTC, but use a different "zero date" or "epoch date")
When I get the date object and print it in mongo shell, it display two different time as follows:
>new Date()
Mon Feb 06 2012 18:49:40 GMT+0530 (IST)
>printjson({created_at: new Date()})
{ created_at : ISODate("2012-02-06T13:19:40.313Z") }
The two times are different, what i am wrong.
This is because of mongodb always store dates in UTC format, but javascript show your local time. And printjson internal mongodb shell function that convert date from your local timezone to utc format. So it shows -5.30 hours backward from your current time.
The times are not different, they are exactly the same! It's merely the same time expressed in different timezones. The "Z" in ISODate means "UTC" (or as some people try to call it: GMT). You're on IST (Indian Standard Time I guess) which is at GMT+0530. 18:49:40 # GMT+5:30 is exactly the same as 13:19 # GMT.
When I run the same code you shown on the shell, I get:
> new Date()
ISODate("2012-02-06T13:34:10.667Z")
As you can see, that is also with "Z". Perhaps you're running an older version of the shell?
cheers,
Derick
I'm using postgresql to store some dates on a database.
In my application it is fundamental that it is completely aware of timezones and I was conducting some basic tests, between, client, server and database.
I'm sending the dates from a browser's application I did in GWT and read the dates on postgresql.
My tests:
The client is always in GMT Timezone, and I'm sending always the same date for each case.
13/04/2012 00:00:00 GMT+00
On posgres I'm changing timezones for each test. Between tests I'm removing all dates from the table.
To change the timezone on the posgres, I do it on the {PostgreSQL HOME}\9.1\data\postgresql.conf setting the timezene to the one I want.
Tests:
Client: 13/04/2012 00:00:00 GMT+00
1st test - posgres EST - 12/04/2012 19:00:00-05
According to postgresql documentation EST = GMT - 5
2nd test - posgres GMT + 5 - 12/04/2012 19:00:00-05
3rd test - posgres GMT - 5 - 13/04/2012 05:00:00+05
Now my question rises: According the the docs, EST = GMT - 5. So why am I reading it the other way around?
Am I missing something here?
EDIT
Technical aspects of my tests:
On the client I send this: 2012 Apr 13 00:00:00 GMT+00.
On the server I'm using JDBC to write on the db: convert java.utils.date to
java.sql.timestamp
java.sql.Timestamp sqlTimeStamp = new java.sql.Timestamp(date.getTime());
(date is java.utils.Date that comes from the client)
set the prepared statement
PreparedStatement ps = con.prepareStatement("INSERT INTO teste.dates (dates_tz, dates_ntz) VALUES (?, ?);"
ps.setTimestamp(1, sqlTimeStamp); ...
For the record, this is just something I want to understand, because overall it works well for my purposes..
Consider that warning in the documentation:
Another issue to keep in mind is that in POSIX time zone names,
positive offsets are used for locations west of Greenwich. Everywhere
else, PostgreSQL follows the ISO-8601 convention that positive
timezone offsets are east of Greenwich.
It looks like the opposite signs towards GMT you're seeing is exactly the effect of that divergence.
The timezone specified in postgresql.conf is probably interpreted with POSIX rules, but it's later displayed by SQL with ISO-8601 rules (the one that anyone really uses).
When the clock on the wall shows 2012-04-13 00:00 in a time zone '+5', the time in London (GMT or UTC) is 2012-04-12 19:00.
If you live in the USA, your local time zone may be '-5'. When it's midnight there, it is 05:00 in the morning in London.
That's just how it is. This detailed answer about handling of time zones in PostgreSQL may help you understand.
I just want to clarify if I am understanding how dates & time zones work.
Basically, I have a date string #"2008-07-06 12:08:49" that I want to convert to an NSDate. I want this date and time to be in whatever the current user's time zone is set in. So if they are in GMT or HST, it's still 12:08:49.
If I have date in unix form 1215382129 (UTC) and my time zone is set to London (GMT), the outputted date from NSLog() is:
2008-07-06 12:08:49 +0100
If I then change my time zone to Hawaii (HST) and output the same date, I get:
2008-07-06 12:08:49 -1000
This seems to work fine, but I was under the impression to get the time in Hawaiian, I'd have to physically add the time difference (-10hrs) to the unix time stamp. Is this not required then?
Does that mean, whatever date and time a unix time is pointing to, it always points to the same date and time in whatever time zone a user is in?
Hope this makes sense!
Edit
I've just realised (thanks to Kevin Conner!) that in fact NSDateFormatter is creating different unix timestamps for that date string depending on the current timezone! So I was totally wrong!! :-)
Disclaimer, I'm mostly a Java guy. But Cocoa seems to work like the Java library in this regard: Dates are zoneless timestamps. Time zones are in the domain of formatting dates for display. In other words, the internal format doesn't consider time zones, it's all in UTC. Time zones are relatively a convenience for humans, so they are in the display/parsing side.
I noticed there is a setTimeZone: method on NSDateFormatter. Try calling that on your formatter before performing the format.