Introduction
A few days ago, this became necessary because of working hard with date, time and timezone information. The main task is to convert date from one local time to another. Trying to find something useful on the net failed, except for finding a small part of an SFL library. After some cutting and pasting their code, I created a few small classes where everything I need can be found. So, that's the history.
There are only five classes, fully describing the topic. They are:
_time_t | time is stored as long value in human readable form HHMMSSCC, where H = hours, m = minutes, s = seconds, c = centiseconds |
_date_t | date stored as CCYYMMDD, where C = century, Y = year, M = month, D = day |
_datetime_t | multiple inherit from _date_t and _time_t |
_tzinfo | timezone information, just as TIME_ZONE_INFORMATION , but has no name attributes |
_tzlist_t | the main goal of this class is to obtain timezone information from registry |
Selecting the internal format of the _time_t
and _date_t
is the most successful route I can imagine. Small memory requirements, human readability (under debugger), simple comparison, wide range, high resolution (1 cs) made it an ideal solution for business applications.
All classes have a set of overloaded operators which made working with it more comfortable. So, take a look...
_datetime_t dt = _datetime_t::now();
cout << _T("now: ") << dt.fmt() << endl;
cout << _T("two hours and seven minutes later: ") << (
dt + _time_t(2,7,0)).fmt()
<< endl << endl;
if ( dt.time() > _time_t(12,0,0))
{
}
else
{
}
dt.set_date(1,2,2001); dt.set_time(12,0,0); cout << _T("create datetime at 4/1/2001, 14:00:00") << endl;
cout << dt.set(14,0,0,1,4,2001).fmt() << endl;
cout << _T("local time : ") << _time_t::now().fmt() << endl;
cout << _T("gmt time : ") << _time_t::gmt_now().fmt() << endl;
cout << _T("local date : ") << _date_t::now().fmt() << endl;
cout << _T("gmt date : ") << _date_t::now().fmt() << endl;
cout << _T("local dateime : ") << _datetime_t::now().fmt() << endl;
cout << _T("gmt datetime : ") << (_datetime_t::gmt_now()).fmt() << endl <<
endl;
_tzinfo_t tzi = _tzinfo_t::current();
cout << _T("convert local datetime to gmt using tzi object") << endl;
cout << _T("gmt dt : ") << tzi.to_gmt(_datetime_t::now()).fmt() << endl <<
endl;
cout << endl << _T("Converting from one local time to another") << endl <<
endl;
_tzlist_t tzlist;
_tzinfo_t tziAfganistan;
_tzinfo_t tziRussian;
_tzinfo_t tziChina;
if (os_version().is_winNT())
{
tziAfganistan = tzlist.get(_T("Afghanistan Standard Time"));
tziRussian = tzlist.get(_T("Russian Standard Time"));
tziChina = tzlist.get(_T("China Standard Time"));
}
else
if (os_version().is_win9x())
{
tziAfganistan = tzlist.get(_T("Afghanistan"));
tziRussian = tzlist.get(_T("Russian"));
tziChina = tzlist.get(_T("China"));
}
else
{
cout << _T("this is Win 3.1, fail to get timezone info") << endl;
return 1;
}
_datetime_t dtAfganistan(22,0,0,28,2,2004);
_datetime_t dtGmt = tziAfganistan.to_gmt(dtAfganistan);
_datetime_t dtRussian = tziRussian.to_local(dtGmt);
_datetime_t dtChina = tziChina.to_local(dtGmt);
cout << _T("afganistan time : ") << dtAfganistan.fmt() << endl;
cout << _T("gmt time : ") << dtGmt.fmt() << endl;
cout << _T("russian time : ") << dtRussian.fmt() << endl;
cout << _T("china time : ") << dtChina.fmt() << endl;
Hope that somebody finds it useful for their projects.
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