C++ store and retrieve UTC time with DST info to/from database

I´m using C++ under Linux and I confess that after reading so many posts on the theme I´m litte confused around time_t, struct tm, time, ctime and strftime.

What I need to do is to get the current system date/time, convert it to UTC and store in database. Later on I need to retrieve that date/time and print on screen in a human readable format.

I´m using Oracle (TIMESTAMP), mySQL (DATETIME) and Sqlite3 (has no datetime field, stored either on a INT or a VARCHAR()).

The most important is that I need to store date/time with current time zone considering the DST time, as when I get back the result I can recover the original time zone of the DST for correct information display.

Something like:

// Get current time 
std::time_t now = std::time(0); 

// Convert it to Oracle ???
? oracletime = ?;

// Convert it to mySQl ???
? mysqltime = ?;

// store it on Sqlite3
int sqlite3time = now;

// print the time
std::cout << now << std::endl;

What would be the correct conversion steps here ?

Thanks for helping.