FHIR Chat · Date/Time comparison · hapi

    BaseDateTimeType me = this;

    // Per FHIRPath rules, we compare equivalence at the lowest precision of the two values,
    // so if we need to, we'll clone either side and reduce its precision
    int lowestPrecision = Math.min(me.getPrecision().ordinal(), theOther.getPrecision().ordinal());
    TemporalPrecisionEnum lowestPrecisionEnum = TemporalPrecisionEnum.values()[lowestPrecision];
    if (me.getPrecision() != lowestPrecisionEnum) {
      me = new DateTimeType(me.getValueAsString());
      me.setPrecision(lowestPrecisionEnum);
    }
    if (theOther.getPrecision() != lowestPrecisionEnum) {
      theOther = new DateTimeType(theOther.getValueAsString());
      theOther.setPrecision(lowestPrecisionEnum);
    }

    if (me.hasTimezoneIfRequired() != theOther.hasTimezoneIfRequired()) {
      if (me.getPrecision() == theOther.getPrecision()) {
        if (me.getPrecision().ordinal() >= TemporalPrecisionEnum.MINUTE.ordinal() && theOther.getPrecision().ordinal() >= TemporalPrecisionEnum.MINUTE.ordinal()) {
          boolean couldBeTheSameTime = couldBeTheSameTime(me, theOther) || couldBeTheSameTime(theOther, me);
          if (!couldBeTheSameTime) {
            return false;
          }
        }
      }
      return null;
    }

    // Same precision
    if (me.getPrecision() == theOther.getPrecision()) {
      if (me.getPrecision().ordinal() >= TemporalPrecisionEnum.MINUTE.ordinal()) {
        long leftTime = me.getValue().getTime();
        long rightTime = theOther.getValue().getTime();
        return leftTime == rightTime;
      } else {
        String leftTime = me.getValueAsString();
        String rightTime = theOther.getValueAsString();
        return leftTime.equals(rightTime);
      }
    }

   * This method returns:
   * <ul>
   *     <li>true if the given datetimes represent the exact same instant with the same precision (irrespective of the timezone)</li>
   *     <li>true if the given datetimes represent the exact same instant but one includes milliseconds of <code>.[0]+</code> while the other includes only SECONDS precision (irrespecitve of the timezone)</li>
   *     <li>true if the given datetimes represent the exact same year/year-month/year-month-date (if both operands have the same precision)</li>
   *     <li>false if both datetimes have equal precision of MINUTE or greater, one has no timezone specified but the other does, and could not represent the same instant in any timezone</li>
   *     <li>null if both datetimes have equal precision of MINUTE or greater, one has no timezone specified but the other does, and could potentially represent the same instant in any timezone</li>
   *     <li>false if the given datetimes have the same precision but do not represent the same instant (irrespective of timezone)</li>
   *     <li>null otherwise (since these datetimes are not comparable)</li>
   * </ul>