stringdate converts dates and timestamps from text to the internal
    DATETIME type.The external format is: YYYY.MM.DD  hh:mm.ss uuuuuu
    where uuuuuu represents number of microseconds.If trailing parts are omitted from the string given to stringdate,
    they are assumed to be zero. The three first parts are mandatory.
    Note that use of cast (x as datetime) is preferred
    over this function.