Rails - Feb 2012 - Time locale / UTC question ? need someone to confirm ...

all my date ties are stored with the standard :db format and being in
western Europe,  I have an UTC offset +1
> Time.now.at_beginning_of_day
 => 2012-02-07 00:00:00 +0100

I''ld like to know if I am right ( or wrong) in my date time based
queries  like :

  scope :today, lambda {
    where("created_at >= ? AND created_at < ? ",
Time.now.at_beginning_of_day, Time.now.tomorrow.at_beginning_of_day)
  }

which generates:
SELECT `event_logs`.* FROM `event_logs` WHERE (created_at
>''2012-02-06 23:00:00'' AND < ''2012-02-07
23:00:00'' )

--------------
OR should I use the Time.now.utc to cope with the :db format ?

  scope :today, lambda {
    where("created_at >= ? AND created_at < ? ",
Time.now.utc.at_beginning_of_day,
Time.now.utc.tomorrow.at_beginning_of_day)
  }
which generates:
SELECT `event_logs`.* FROM `event_logs` WHERE (created_at
>''2012-02-07 00:00:00'' AND created_at <
''2012-02-08 00:00:00'' )

my guess is the 2nd scope , but I am not sure

thanks for your feedback

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On 7 February 2012 17:12, Erwin <yves_dufour-ee4meeAH724@public.gmane.org>
wrote:
> all my date ties are stored with the standard :db format and being in
> western Europe,  I have an UTC offset +1
>
>> Time.now.at_beginning_of_day
>  => 2012-02-07 00:00:00 +0100
>
> I''ld like to know if I am right ( or wrong) in my date time based
> queries  like :
>
>  scope :today, lambda {
>    where("created_at >= ? AND created_at < ? ",
> Time.now.at_beginning_of_day, Time.now.tomorrow.at_beginning_of_day)
>  }
>
> which generates:
> SELECT `event_logs`.* FROM `event_logs` WHERE (created_at >>
''2012-02-06 23:00:00'' AND < ''2012-02-07
23:00:00'' )
>
> --------------
> OR should I use the Time.now.utc to cope with the :db format ?
>
>  scope :today, lambda {
>    where("created_at >= ? AND created_at < ? ",
> Time.now.utc.at_beginning_of_day,
> Time.now.utc.tomorrow.at_beginning_of_day)
>  }
> which generates:
> SELECT `event_logs`.* FROM `event_logs` WHERE (created_at >>
''2012-02-07 00:00:00'' AND created_at < ''2012-02-08
00:00:00'' )
>
> my guess is the 2nd scope , but I am not sure
It depends which you want.  Times in the db should always be in UTC,
so in the first case it is testing against the start of the day in
local time, which is 23:00 UTC.  In the second case it is testing
against the start of the day UTC.  So the decision is yours, if you
want your scope to return events from today local time then use the
former, if you want today UTC then use the later.  It all depends on
what you mean by ''today''.

Colin

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Colin Law wrote in post #1044565:
> On 7 February 2012 17:12, Erwin
<yves_dufour-ee4meeAH724@public.gmane.org> wrote:
> It depends which you want.  Times in the db should always be in UTC,
> so in the first case it is testing against the start of the day in
> local time, which is 23:00 UTC.  In the second case it is testing
> against the start of the day UTC.  So the decision is yours, if you
> want your scope to return events from today local time then use the
> former, if you want today UTC then use the later.  It all depends on
> what you mean by ''today''.
And, by "local time" he means "server''s local time"
not necessarily the
"local time" for the actual user. If you want to support the
"user''s
local time" then you''ll need to know the time zone where the user 
actually resides. Typically that''s just something you''ll have
to ask
them when they create their account so you can store their local time 
zone along with their account information.

Ughhh! +1 for Stardates.

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Thanks Robert & Colin, in the current case , server and users are in
the same Time zone  ( UTC+1) so server local time is user local time
( my UNIX box is UTC+1)

by today , I always mean  user''s today  which is local time
so as per your answer when I make a  local time query, it''s normal to
have it ''converted'' into utc for comparisons

so  =>   all events are created at user''s local time , then stored
in
UTC
if I need to query last week  user''s events, then my query should use
local  time ( system will convert the query times to UTC and compare
with stored db UTC  times)

thanks again

On Feb 7, 7:18 pm, Robert Walker
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> Colin Law wrote in post #1044565:
>
> > On 7 February 2012 17:12, Erwin
<yves_duf...-ee4meeAH724@public.gmane.org> wrote:
> > It depends which you want.  Times in the db should always be in UTC,
> > so in the first case it is testing against the start of the day in
> > local time, which is 23:00 UTC.  In the second case it is testing
> > against the start of the day UTC.  So the decision is yours, if you
> > want your scope to return events from today local time then use the
> > former, if you want today UTC then use the later.  It all depends on
> > what you mean by ''today''.
>
> And, by "local time" he means "server''s local
time" not necessarily the
> "local time" for the actual user. If you want to support the
"user''s
> local time" then you''ll need to know the time zone where the
user
> actually resides. Typically that''s just something you''ll
have to ask
> them when they create their account so you can store their local time
> zone along with their account information.
>
> Ughhh! +1 for Stardates.
>
> --
> Posted viahttp://www.ruby-forum.com/.
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On Tue, Feb 7, 2012 at 6:12 PM, Erwin
<yves_dufour-ee4meeAH724@public.gmane.org> wrote:
> all my date ties are stored with the standard :db format and being in
> western Europe,  I have an UTC offset +1
>
> > Time.now.at_beginning_of_day
>  => 2012-02-07 00:00:00 +0100
>
> I''ld like to know if I am right ( or wrong) in my date time based
> queries  like :
>
>  scope :today, lambda {
>    where("created_at >= ? AND created_at < ? ",
> Time.now.at_beginning_of_day, Time.now.tomorrow.at_beginning_of_day)
>  }
>
> which generates:
> SELECT `event_logs`.* FROM `event_logs` WHERE (created_at >>
''2012-02-06 23:00:00'' AND < ''2012-02-07
23:00:00'' )
>
> --------------
> OR should I use the Time.now.utc to cope with the :db format ?
>
>  scope :today, lambda {
>    where("created_at >= ? AND created_at < ? ",
> Time.now.utc.at_beginning_of_day,
> Time.now.utc.tomorrow.at_beginning_of_day)
>  }
> which generates:
> SELECT `event_logs`.* FROM `event_logs` WHERE (created_at >>
''2012-02-07 00:00:00'' AND created_at < ''2012-02-08
00:00:00'' )
>
> my guess is the 2nd scope , but I am not sure
>
> thanks for your feedback
>
Just curious, could you not juet use Date (instead of Time).

E.g. for contract start and end dates and programming that for an
international company in a previous life, I had changed back certain
fields from the initial choice of "time" (as seemed obvious because
of the default for "created_at" etc.) to "date"
(Contract#starts_date
and Contract#end_date).

So, it was then trivial to compare, understand and display the
date to the users. For the abstract concept of a "date", I learned
the hard way to use a Date (and not Time).

So, maybe your database could have a column "creation_date"
that is really a Date and that is initialized when the record is
created in the local time zone of the user for which the Date
has a "real-life" sense. And then the start_date or creation_date
of e.g. his/her membership has an obvious local meaning.

Just my 2 cents (and venting some old frustrations I suffered over this ...)

HTH,

Peter

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Hi Peter

I understand ... I dream about a format  Date  + am:pm  !   ( created
in the morning or created in the afternoon...)   LOL

more, I need Time....  actually I need to split events into morning /
afternoon events  ( half day am:pm  )
projects have half-day tasks only..
I found very useful the business_days gem, but nothing regarding
am:pm management.....


On Feb 7, 11:38 pm, Peter Vandenabeele
<pe...-jNuWw7i2w7syMbTcgqFhxg@public.gmane.org>
wrote:
> On Tue, Feb 7, 2012 at 6:12 PM, Erwin
<yves_duf...-ee4meeAH724@public.gmane.org> wrote:
> > all my date ties are stored with the standard :db format and being in
> > western Europe,  I have an UTC offset +1
>
> > > Time.now.at_beginning_of_day
> >  => 2012-02-07 00:00:00 +0100
>
> > I''ld like to know if I am right ( or wrong) in my date time
based
> > queries  like :
>
> >  scope :today, lambda {
> >    where("created_at >= ? AND created_at < ? ",
> > Time.now.at_beginning_of_day, Time.now.tomorrow.at_beginning_of_day)
> >  }
>
> > which generates:
> > SELECT `event_logs`.* FROM `event_logs` WHERE (created_at >>
> ''2012-02-06 23:00:00'' AND < ''2012-02-07
23:00:00'' )
>
> > --------------
> > OR should I use the Time.now.utc to cope with the :db format ?
>
> >  scope :today, lambda {
> >    where("created_at >= ? AND created_at < ? ",
> > Time.now.utc.at_beginning_of_day,
> > Time.now.utc.tomorrow.at_beginning_of_day)
> >  }
> > which generates:
> > SELECT `event_logs`.* FROM `event_logs` WHERE (created_at >>
> ''2012-02-07 00:00:00'' AND created_at <
''2012-02-08 00:00:00'' )
>
> > my guess is the 2nd scope , but I am not sure
>
> > thanks for your feedback
>
> Just curious, could you not juet use Date (instead of Time).
>
> E.g. for contract start and end dates and programming that for an
> international company in a previous life, I had changed back certain
> fields from the initial choice of "time" (as seemed obvious
because
> of the default for "created_at" etc.) to "date"
(Contract#starts_date
> and Contract#end_date).
>
> So, it was then trivial to compare, understand and display the
> date to the users. For the abstract concept of a "date", I
learned
> the hard way to use a Date (and not Time).
>
> So, maybe your database could have a column "creation_date"
> that is really a Date and that is initialized when the record is
> created in the local time zone of the user for which the Date
> has a "real-life" sense. And then the start_date or creation_date
> of e.g. his/her membership has an obvious local meaning.
>
> Just my 2 cents (and venting some old frustrations I suffered over this
...)
>
> HTH,
>
> Peter
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On Wed, Feb 8, 2012 at 10:02 AM, Erwin
<yves_dufour-ee4meeAH724@public.gmane.org> wrote:
> Hi Peter
>
> I understand ... I dream about a format  Date  + am:pm  !   ( created
> in the morning or created in the afternoon...)   LOL
>
That would be:

am = DayTimeRange.new("00:00 until 12:00")
pm = DayTimeRange.new("12:00 until 24:00")

(https://github.com/petervandenabeele/relativity)

As I write this, I see I should introduce a "00:00...12:00"
variant (with 3 dots), which includes the 00:00, but ends
just before 12:00 (actually, is 12:00:00.000000000
am or pm ? I presume it is pm).


> more, I need Time....  actually I need to split events into morning /
> afternoon events  ( half day am:pm  )
> projects have half-day tasks only..
> I found very useful the business_days gem, but nothing regarding
> am:pm management.....
>
HTH,

Peter

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