Re: [Cppcms-users] How to store/manipulate dates?

[Artyom B. <art...@ya...>]

Let's make an order:

std::time_t - number POSIX time general time representation, time zone
  independent


booster::ptime - POSIX time - general time representation as a number
  similar to time_t but with higher precision.

  Time zone independent.


booster::locale::date_time - localized time representation. Internally
  similar to time_t but allows operations according to current locale
  for example what is the first day of this week which maybe Sunday
  or Monday according to the locale (US/FR)

  Internally time zone independent but operations are time zone dependent.

  Requires special locale for operations (not necessary global)

std::tm Standard C++ date-time representation. Does not hold and information
  about time zone.

So which one do you need?



if you want to use ptime with cppdb:

   p = booster::ptime::universal_time(get<std::tm>(column))
   p = booster::ptime::local_time(get<std::tm>(column))

   statement.bind(booster::ptime::universal_time(p));
   statement.bind(booster::ptime::local_time(p));

If you want to use boost::locale::date_time with cppdb,
you need to convert it into std::tm or from std::tm

Usually it is not stright-forward as date_time may use
for example Hebrew or Japanese calendar and the conversion
to std::tm would not be correct as Gregorian month
and Hebrew month are different. So you need to convert it first
to either time_t or booster::ptime and then to std::tm
and the other way around.

Of course you can set std::tm's fields manually if you know
that boost::locale::date_time uses Gregorian calendar.
 
If you want to store only date you have two options:

Use string and format it as "YYYY-MM-DD" or
use std::tm with relevant fields set if the SQL engine
knows to convert one type to another.


Artyom Beilis
--------------
CppCMS - C++ Web Framework:   http://cppcms.com/
CppDB - C++ SQL Connectivity: http://cppcms.com/sql/cppdb/


>________________________________
> From: "ele...@ex..." <ele...@ex...>
>To: cpp...@li... 
>Sent: Monday, February 6, 2012 9:36 AM
>Subject: Re: [Cppcms-users] How to store/manipulate dates?
> 
>Ah yes, thank you.
>
>This is what im doing now -
>
>c.topics[i].created_at =
>booster::ptime::local_time(r.get<std::tm>("created_at"));
>
>Next question is - what data type to use for storing only date?
>
>Thanks again
>Petr
>
>> Sorry for the "late" reply.
>> What you are looking for is this
>>
>> http://cppcms.com/cppcms_ref_v0_99/classbooster_1_1ptime.html
>>
>> greetings
>>
>
>
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