mongocxx: Inserting a Datetime

I'm trying to insert a date and time into mongocxx after parsing a data file, my actual datetime is:

2007/12/01 00:00:00

That is, December 1, 2007 at midnight. I have this code:

static bsoncxx::document::value make_doc(sm_struct const sm) {
    std::tm t{0};
    t.tm_sec = 0;
    t.tm_min=(int)sm.minute;
    t.tm_hour=(int)sm.hour;
    t.tm_mday=(int)sm.day-1;
    t.tm_mon=(int)sm.month;
    t.tm_year=sm.year-1900;
    t.tm_isdst = -1;
    std::time_t tt = mktime(&t);

    std::cout << sm.year << " " << t.tm_year << "/" << t.tm_mon << "/" << t.tm_mday << " " << t.tm_hour << ":" << t.tm_min << std::endl;
    bsoncxx::document::value document = bsoncxx::builder::basic::make_document(
        bsoncxx::builder::basic::kvp("datetime", bsoncxx::types::b_date{
            std::chrono::system_clock::from_time_t(tt)
        }),
    );
    return document;
}

Running my code I get this on stdout:

2007 107/11/31 0:0

When I check my date in the database I get:

ISODate("2007-12-30T13:30:00.000+0000")

How come the hours and minutes are not being set correctly here?

Solution

It looks correct you insert Dec 31, 2007 at midnight local time in Adelaide which is Dec 30, 2007 13:30 (UTC). You can convert the UTC time back to your local time when you show it.

Adelaide, Australia    Mon, 31 Dec 2007 at 00:00 ACDT    
UTC, Time Zone         Sun, 30 Dec 2007 at 13:30

Source: timeanddate.com