val dateFormat =
      SimpleDateFormat("yyMMddHHmmss'Z'").apply {
        timeZone = utc
        set2DigitYearStart(Date(-631152000000L)) // 1950-01-01T00:00:00Z.
      }

    return dateFormat.format(date)
  }

  /**
   * A timestamp like "191216030210Z" or "20191215190210-0800" for 2019-12-15T19:02:10-08:00. This
   * is the same as [UTC_TIME] with the exception of the 4-digit year.
   */