checked_set (_hours, lexical_cast<string> (h));
checked_set (_minutes, lexical_cast<string> (m));
checked_set (_seconds, lexical_cast<string> (s));
checked_set (_frames, lexical_cast<string> (f));
checked_set (_hours, lexical_cast<string> (h));
checked_set (_minutes, lexical_cast<string> (m));
checked_set (_seconds, lexical_cast<string> (s));
checked_set (_frames, lexical_cast<string> (f));