No, UTC itself never has DST. It is the constant frame of reference other time zones are expressed relative to.

From the [Wikipedia UTC page][1]:

&gt; UTC does not change with a change of seasons, but local time or civil time may change if a time zone jurisdiction observes daylight saving time or summer time. For example, UTC is 5 hours ahead of local time on the east coast of the United States during winter, but 4 hours ahead during summer.

In other words, when a time zone observes DST, its offset from UTC changes when there&#39;s a DST transition, but that&#39;s *that time zone* observing DST, not UTC.

Without knowing much about PHP time zone handling, it seems strange to me that you can specify &quot;with DST&quot; or &quot;without DST&quot; in a conversion - the time zones themselves specify when DST kicks in... it shouldn&#39;t have to be something you specify yourself.

  [1]: http://en.wikipedia.org/wiki/Coordinated_Universal_Time

I&#39;m having the same issue, using this code:

    date_default_timezone_set(&#39;UTC&#39;);
    $nowdate = date(&#39;l jS \of F Y h:i:s A&#39;);
    echo &quot;Current date and time is: &quot; . $nowdate;

It is summer now, and the time this code produces is one hour behind - so I don&#39;t think that UTC time in PHP adjusts to DST.

Be interesting to see if anyone has the solution...

EDIT:

Found this code on a forum, works perfectly!!

    date_default_timezone_set(&#39;Europe/London&#39;);
    $TIME =  date(&quot;m/d/Y H:i&quot;,time());

So you can then call the current date and time by using $TIME.
The output can be adjusted to display it differently by changing the bit inside the date() tag.
If you want to adjust the date() output, use this guide: http://php.net/manual/en/function.time.php

Hope this helps :)

If we have two activities:

 1. List of files and last modified time
 2. File editing activity

A user selects a file from the list and is taken to the file editing activity. When done editing, the user presses the back button to return to the file list.

The list is not reloaded and therefore an incorrect value is displayed for the just edited files modified time.

What is the proper method of causing the file list to refresh after the back button is pressed? 

This example assumes that no database is being used, just an ArrayAdapter.



Back button and refreshing previous activity

I am trying to replicate an example found on MSDN. I am using ASP.NET and EF 4.1 (CTP?). I&#39;ve used NuGet to install the EntityFramework package.

I am getting this error: `The provider did not return a ProviderManifestToken string` ...
and the database is never created.

Here is my connection string:

    &lt;add name=&quot;HospitalContext&quot;
       connectionString=
       &quot;data source=.\SQLExpress;initial catalog=NewTestDB;integrated security=True;&quot;
       providerName=&quot;System.Data.SqlClient&quot;/&gt;

Here is my code:

    var pat = new Patient { Name = &quot;Shane123132524356436435234&quot; };
    db.Patients.Add(pat);

    var labResult = new LabResult { Result = &quot;bad&quot;, Patient = pat };
          
    int recordAffected = db.SaveChanges();

Here is my context:

    public class HospitalContext : DbContext
    {
        static HospitalContext()
        {
            Database.SetInitializer(new HostpitalContextInitializer());
        }

        public DbSet&lt;Patient&gt; Patients { get; set; }
        public DbSet&lt;LabResult&gt; LabResults { get; set; }
    }

    public class HostpitalContextInitializer :
                 DropCreateDatabaseIfModelChanges&lt;HospitalContext&gt;
    {
        protected override void Seed(HospitalContext context)
        {
            context.Patients.Add(new Patient { Name = &quot;Fred Peters&quot; });
            context.Patients.Add(new Patient { Name = &quot;John Smith&quot; });
            context.Patients.Add(new Patient { Name = &quot;Karen Fredricks&quot; });
        }
    }

This is a fully patched SQL 2008 system, with VS 2010 SP1.


EF 4.1 exception &quot;The provider did not return a ProviderManifestToken string&quot;

I am trying to write a script where i want to convert any timezone to `UTC` and reverse.
But  from some where i came to know that while converting any timezone to `UTC`  with or without DST consideration it will give the same `UTC` time.
For example:
If i try to convert this one:

    $mytime = &#39;2011-03-31 05:06:00.000&#39;;
    $myzone = &#39;America/New_York&#39;;


to UTC with DST and without DST,i will get ..


    (New_York-&gt;UTC DST=Yes)2011-03-31 09:06:00
    (New_York-&gt;UTC DST=No)2011-03-31 09:06:00 ..........

Is this corect ??If yes then why???
Please anybody give me your answers.

Does UTC observe daylight saving time?

I am trying to write a script where i want to convert any timezone to <code>UTC</code> and reverse.
But from some where i came to know that while converting any timezone to <code>UTC</code> with or without DST consideration it will give the same <code>UTC</code> time.
For example:
If i try to convert this one:
<pre><code class="hljs language-ini">$mytime = '2011-03-31 05:06:00.000';
$myzone = 'America/New_York';
</code></pre>
to UTC with DST and without DST,i will get ..
<pre><code class="hljs language-ini">(New_York->UTC DST=Yes)2011-03-31 09:06:00
(New_York->UTC DST=No)2011-03-31 09:06:00 ..........
</code></pre>
Is this corect ??If yes then why???
Please anybody give me your answers.

How can I convert the output of PHP&#39;s `filesize()` function to a nice format with MegaBytes, KiloBytes etc?

like:

- if the size is less than 1 MB, show the size in KB
- if it&#39;s between 1 MB - 1 GB show it in MB
- if it&#39;s larger - in GB


PHP filesize MB/KB conversion

I am trying to debug some PHP code and wanted to download the XDebug debugger for PHP.  All I see there is Windows binaries for downloading.  Is it at all possible to use it on Ubuntu?

Is it possible to use xdebug on Ubuntu?

I&#39;m not too good with regular expressions, but with PHP I&#39;m wanting to remove the `style` attribute from HTML tags in a string that&#39;s coming back from TinyMCE.

So change `&lt;p style=&quot;...&quot;&gt;Text&lt;/p&gt;` to just vanilla `&lt;p&gt;Test&lt;/p&gt;`.

How would I achieve this with something like the `preg_replace()` function?

Remove style attribute from HTML tags

I&#39;m implementing a REST service in PHP. This service should be able to support multiple input and output formats (JSON, XML). For that reason I want to check the request headers *&quot;Accept&quot;* and *&quot;Content-Type&quot;* for the type of content sent and requested by the client.

Accessing the *&quot;Accept&quot;* header is a simple as using `$_SERVER[&#39;HTTP_ACCEPT&#39;]`. But accessing the *&quot;Content-Type&quot;* header seems to be a difficult task. I searched the PHP documentation and the web, but the only solution offered was the use of the PHP function `apache_request_headers()` which is only supported when PHP is installed as an Apache module, which is not true in my case.

So my question now: How can I access the header &quot;Content-Type&quot; of a request?

Get &quot;Content-Type&quot; header of request in PHP

I have a 404.php file in my site&#39;s main directory and I was using `header(&#39;Location: 404.php&#39;);` for a while until someone said that you should use `header(&#39;HTTP/1.0 404 Not Found&#39;);` instead. So I replaced it with that and then added: `ErrorDocument 404 /404.php` to my apache config file and restarted the server but it doesn&#39;t work.

I tried different variations including `ErrorDocument 404 404.php` and `ErrorDocument 404 mywebite/404.php` but to no avail.

What I mean by doesn&#39;t work is that earlier when using `header(&#39;Location: 404.php&#39;);` it would redirect to the 404.php file but when I replace it with `header(&#39;HTTP/1.0 404 Not Found&#39;);` it seems to just skip over the line and not do anything. It most certainly is not redirecting. The reason I am calling for the redirect is because if a $_GET header value is not recognized the page should 404.

header(&#39;HTTP/1.0 404 Not Found&#39;); not doing anything

- Operating system: Linux

- Filesystem type: [ext3][1]

- Preferred solution: Bash (script/one-liner), Ruby, or Python

I have several directories with several subdirectories and files in them. I need to make a list of all these directories that is constructed in a way such that every first-level directory is listed next to the date and time of the latest created/modified file within it.

To clarify, if I touch a file or modify its contents a few subdirectory levels down, that timestamp should be displayed next to the first-level directory name. Say I have a directory structured like this:

    ./alfa/beta/gamma/example.txt

and I modify the contents of the file `example.txt`, I need that time displayed next to the first-level directory `alfa` in human readable form, not epoch. I&#39;ve tried some things using find, [`xargs`][2], [`sort`][3] and the like, but I can&#39;t get around the problem that the filesystem timestamp of &#39;alfa&#39; doesn&#39;t change when I create/modify files a few levels down.

  [1]: https://en.wikipedia.org/wiki/Ext3
  [2]: https://en.wikipedia.org/wiki/Xargs
  [3]: https://en.wikipedia.org/wiki/Sort_(Unix)





How to recursively find and list the latest modified files in a directory with subdirectories and times

How do you calculate program run time in python?

I am using `system.time(expression)` to measure execution time for an R function.

The output I get for the call

    system.time(myfunction())

is:

        user  system elapsed   
      117.36    5.65  127.86

What does &#39;user&#39; and &#39;system&#39; measure?

What are &#39;user&#39; and &#39;system&#39; times measuring in R system.time(exp) output?

I&#39;m working with a code that gives me utc timestamps and I want to convert them to appropriate datetimes.   Unfortunately when I test simple cases with pytz the datetime has an added 6 hours (the CST offset to UTC).  I need to keep timezone data correct because I am calculating difference between other timezones as well.  Any ideas why and how to convert a utc timestamp to a utc datetime?


    In [1]: import pytz
    
    In [2]: from datetime import datetime
    
    In [3]: import time
    
    In [4]: datetime.fromtimestamp(time.mktime(datetime(7,1,1, tzinfo=pytz.UTC).timetuple()), tz=pytz.UTC)
    Out[4]: datetime.datetime(2007, 1, 1, 6, 0, tzinfo=&lt;UTC&gt;)
    
    In [5]: datetime.fromtimestamp(time.mktime(datetime(7,1,1).utctimetuple()), tz=pytz.UTC)
    Out[5]: datetime.datetime(2007, 1, 1, 6, 0, tzinfo=&lt;UTC&gt;)
    
    In [6]: datetime.fromtimestamp(time.mktime(datetime(7,1,1).utctimetuple()))
    Out[6]: datetime.datetime(2007, 1, 1, 0, 0)



Converting python datetime to timestamp and back in UTC still uses local timezone

How can I get the current time in milliseconds in Python? 

Get current time in milliseconds in Python?

Generally, it is the best practice to store time in UTC and as mentioned in [here][1] and [here][2].

Suppose there is a re-occurring event let&#39;s say end time which is always at the same local time let&#39;s say 17:00 regardless of whether there is Daylight saving is on or off for that time zone. And also there is a requirement not to change the time manually when DST turns ON or OFF for particular time zone. It is also a requirement that whenever end time is asked by any other systems through API (i.e. GetEndTimeByEvent) it always sends the end time in UTC format.

**Approach 1:**
If it is decided **to store in UTC** it can be stored in the database table as below. 

    Event      UTCEndTime
    =====================
    ABC	        07:00:00
    MNO	        06:00:00
    PQR	        04:00:00

For the first event ABC, end time in UTC is 07:00 am which if converted to display from UTC to local time on 1-July-2012 it will result into 17:00 local time and if converted on 10-Oct-2012 (the date when DST is ON for the time zone) then will result into 6 pm which is not correct end time.

One possible way I could think is to store DST time in the additional column and using that time when the timezone has DST ON.

**Approach 2:**
However,  if it is **stored as Local time** as below for example for event ABC it will be always 17:00 on any date as there is no conversion to from UTC to local time. 

    Event      LocalEndTime
    =======================
    ABC	        17:00:00
    MNO	        16:00:00
    PQR	        14:00:00

And an application layer converts local time to UTC time to send to other systems through (API GetEndTimeByEvent).

**Is this still a good idea to store the time in UTC in this case? If yes then how to get a constant local time?**

Related Questions: https://stackoverflow.com/questions/1127781/is-there-ever-a-good-reason-to-store-time-not-in-utc?rq=1


  [1]: https://stackoverflow.com/questions/2532729/daylight-saving-time-and-timezone-best-practices/
  [2]: https://stackoverflow.com/a/5667869/19917

Is it always a good idea to store time in UTC or is this the case where storing in local time is better?

This is a bit of my JS code for which this is needed:

    var secDiff = Math.abs(Math.round((utc_date-this.premiere_date)/1000));
    this.years = this.calculateUnit(secDiff,(86400*365));
    this.days = this.calculateUnit(secDiff-(this.years*(86400*365)),86400);
    this.hours = this.calculateUnit((secDiff-(this.years*(86400*365))-(this.days*86400)),3600);
    this.minutes = this.calculateUnit((secDiff-(this.years*(86400*365))-(this.days*86400)-(this.hours*3600)),60);
    this.seconds = this.calculateUnit((secDiff-(this.years*(86400*365))-(this.days*86400)-(this.hours*3600)-(this.minutes*60)),1);

I want to get the datetime in &quot;ago&quot;, but if the DST is in use then the dates are off by 1 hour. I don&#39;t know how to check if the DST is in effect or not.

How can I know when the daylight saving starts and ends?

How to check if DST (Daylight Saving Time) is in effect, and if so, the offset?

There were quite a few questions about saving datetime &amp; timezones info in DB but more on the overall level. Here I&#39;d like to address a specific case.

**System specs**

 - We have an Orders system database
 - It is a multi-tenant system where tenants can use arbitrary timezone (it is arbitrary but single timezone per tenant, saved in Tenants table once and never changes)

**Business rule needed to be covered in DB**
  
  - When tenant places an Order into the system, **order number gets computed based on their local datetime** (its not literally a number but some kind of an identifier like `ORDR-13432-Year-Month-Day`). Precise calculation is not important for the moment, it&#39;s just important that it&#39;s dependant on tenants local datetime
  - We also do want to be able to select all Orders, on the system level, placed between some UTC datetimes regardless of the tenant (for general system statistics/reporting)

**Our initial idea**

  - Our initial idea was to save UTC datetime across whole DB and, of course, keep tenants timezone offset relative to UTC and have application that consumes DB always convert datetimes to UTC so that DB itself always operate with UTC.

**Approach 1**

  - Saving local tenants datetime would be nice per tenant but then we have problem with queries like: 

        SELECT * FROM ORDERS WHERE OrderDateTime BETWEEN UTCDateTime1 AND UTCDateTime2

It&#39;s problematic because `OrderDateTime` in this query means different moment in time, based on tenant. Of course, this query might include join to `Tenants` table to get local datetime offset which would then calculate `OrderDateTime` on the fly to make adjustments. It&#39;s possible, but not sure if it&#39;s a good way to do it?

**Approach 2**

  - On the other hand, when saving UTC datetime, then when we do calculation of OrderNumber since the day/month/year in UTC might differ from the one in local datetime

Let&#39;s take extreme example; let&#39;s say tenant is 6 hours ahead of UTC and his local datetime is `2017-01-01 02:00`. 
UTC would be `2016-12-31 20:00`. Order placed at that moment should get OrderNumber `&#39;ORDR-13432-2017-1-1&#39;` but if saving UTC it would get `ORDR-13432-2016-12-31`.

In this case, at the moment of creating Order in DB, we should get UTC datetime, tenants offset and compile OrderNumber based on recalculated tenants localtime but still save DateTime column in UTC.


**Questions**

 1. What is the preferred way of handling this kind of situation?
 2. Is there a nice solution with saving UTC datetimes because that one would be pretty nice for us because of the system-level reporting?
 3. If going with saving UTC, is Approach 2) good way to handle those cases or is there some better/recommended way?

**[UPDATE]**

Based on comments from Gerard Ashton and Hugo:

Initial question was not clear with respect to the detail if tenant can change timezone or not and what happens if political authority changes the timezone properties or some terirory&#39;s timezone. 
Of course that is of an extreme importance, but it is not in the center of this question . We might address that in a separate question.

For the sake of this question, lets assume tenant will not change location. Timezone properties or timezone itself for that location might change and those changes will be handled in the system separately from this question.

Content Type	Original Author	Original Content on Stackoverflow
Question	0001	View Question on Stackoverflow
Solution 1 - Php	Jon Skeet	View Answer on Stackoverflow
Solution 2 - Php	MattFiler	View Answer on Stackoverflow

Does UTC observe daylight saving time?

Php Problem Overview

Php Solutions

Solution 1 - Php

Solution 2 - Php

EF 4.1 exception "The provider did not return a ProviderManifestToken string"

Back button and refreshing previous activity

Attributions