code: func TimestampDiff(unit string, t1 Time, t2 Time) int64 {
  	return timestampDiff(unit, t1.Time, t2.Time)
  }
docs: // TimestampDiff returns t2 - t1 where t1 and t2 are date or datetime expressions.
  // The unit for the result (an integer) is given by the unit argument.
  // The legal values for unit are "YEAR" "QUARTER" "MONTH" "DAY" "HOUR" "SECOND" and so on.