code: @Nullable
      public Date getDateDigitized(@Nullable TimeZone timeZone)
      {
          TimeZone timeZoneDigitized = getTimeZone(TAG_OFFSET_TIME_DIGITIZED);
          return getDate(TAG_DATETIME_DIGITIZED, getString(TAG_SUBSECOND_TIME_DIGITIZED),
              (timeZoneDigitized != null) ? timeZoneDigitized : timeZone);
      }
docs: Parses the date/time tag, the subsecond tag and the time offset tag to obtain a single Date
  object with milliseconds representing the date and time when this image was digitized.  If
  the time offset tag does not exist, attempts will be made to parse the values as though it is
  in the {@link TimeZone} represented by the {@code timeZone} parameter (if it is non-null).
  
  @param timeZone the time zone to use
  @return A Date object representing when this image was digitized, if possible, otherwise null