code: public static ZonedDateTime toZonedDateTimeUtc(final long epoch) {
          final EpochUnits units = EpochUnits.valueOf(epoch);
          return toZonedDateTimeUtc(epoch, units);
      }
docs: Returns a <code>ZonedDateTime</code> from the given epoch value.
  
  Note that this implementation attempts to protect against caller providing timestamps in
  different units. For example, Unix timestamps are the number of SECONDS since January 1,
  1970, while Java Dates are number of MILLISECONDS since January 1, 1970.
  
  @param epoch
  timestamp value in seconds, milliseconds or microseconds
  @return a <code>ZonedDateTime</code> or null if the date is not valid