A Few Classes to Work With Date, Time, Datetime and Timezone Data

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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:

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...

//local time
_datetime_t dt = _datetime_t::now(); 
cout << _T("now: ") << dt.fmt() << endl;

//add two hour, seven minutes
cout << _T("two hours and seven minutes later: ") << (
    dt + _time_t(2,7,0)).fmt() 
     << endl << endl;

//comparing
if ( dt.time() > _time_t(12,0,0))
{
    //before 12:00:00
}
else
{
    //after 
}

//assigning
dt.set_date(1,2,2001); //2/1/2001
dt.set_time(12,0,0); //12:00:00
cout << _T("create datetime at 4/1/2001, 14:00:00") << endl;
cout << dt.set(14,0,0,1,4,2001).fmt() << endl;

//few static function to get current time, date info
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;

//create timezone information object
_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;

//now let's do what this classes is created for - converting from one local
//time to another for example convert local afganistan time to local russian 
//time and china

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;
}
//set local afganistan time - 12:00:00, 2/1/2001
_datetime_t dtAfganistan(22,0,0,28,2,2004);
    
//convert to gmt
_datetime_t dtGmt = tziAfganistan.to_gmt(dtAfganistan);
    
//convert it to other local times 
_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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