This function adds a new metadata name-value-type tuple to a designated name-value record.
The struct tm fields are as defined in the POSIX standard and interpreted by mktime(3C). All fields are ignored except:
int tm_mday; /* day of the month - [1, 31] */ int tm_mon; /* months since January - [0, 11] */ int tm_year; /* years since 1900 */
The name-value record automatically expands as needed. The name and value are copied into the structure.