code: func NewDateTimeFieldDescriptor(nullable NullableColumn) FieldDescriptor {
  	return newFixedLengthFieldDescriptor(
  		mysql_proto.FieldType_DATETIME,
  		nullable,
  		8,
  		func(b []byte) interface{} {
  			val := LittleEndian.Uint64(b)
  			d := val / 1000000
  			t := val % 1000000
  			return time.Date(
  				int(d/10000),              // year
  				time.Month((d%10000)/100), // month
  				int(d%100),                // day
  				int(t/10000),              // hour
  				int((t%10000)/100),        // minute
  				int(t%100),                // second
  				0,                         // nanosecond
  				time.UTC)
  		})
  }
docs: // This returns a fields descriptor for FieldType_DATETIME
  // (i.e., Field_datetime).  See number_to_datetime (in sql-common/my_time.c)
  // for encoding detail.