CHARACTER_LENGTH(datetime) returns wrong length

A date time returns a string similar to "1997-01-01 00:00:00", which has 19 characters, yet the function CHARACTER_LENGTH when passed a date-time object returns 7 fewer. This is because of the following specific code in the function:

//adjust for microseconds not counted
return (int64_t)date.size() - 7;

Not sure why this is there as microseconds have nothing to do with it.