public static final String ISO_DATETIME_FORMAT = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";

    /** Date optional time format identifier. */
    public static final String DATE_OPTIONAL_TIME = "date_optional_time";

    // ============================================================
    // Default Values and Status
    // ============================================================

        "type": "long"
      },
      "created": {
        "type": "date",
        "format": "date_optional_time"
      },
      "timestamp": {
        "type": "date",
        "format": "date_optional_time"
      },
      "expires": {
        "type": "date",
        "format": "date_optional_time"
      },
      "digest": {
        "type": "text",
        "index": false
      },

        "type": "long"
      },
      "created": {
        "type": "date",
        "format": "date_optional_time"
      },
      "timestamp": {
        "type": "date",
        "format": "date_optional_time"
      },
      "expires": {
        "type": "date",
        "format": "date_optional_time"
      },
      "digest": {
        "type": "text",
        "index": false
      },

        "type": "long"
      },
      "created": {
        "type": "date",
        "format": "date_optional_time"
      },
      "timestamp": {
        "type": "date",
        "format": "date_optional_time"
      },
      "expires": {
        "type": "date",
        "format": "date_optional_time"
      },
      "digest": {
        "type": "text",
        "index": false
      },

     * @param value the date string to parse
     * @return parsed Date object, or null if parsing fails
     */
    public static Date parseDate(final String value) {
        return parseDate(value, Constants.DATE_OPTIONAL_TIME);
    }

    /**
     * Parses a date string using the specified format.
     *
     * @param value the date string to parse
     * @param format the date format pattern or "pdf_date" for PDF date format

                                    dateFormat = Constants.MAPPING_TYPE_PDF_DATE;
                                } else {
                                    dateFormat = Constants.DATE_OPTIONAL_TIME;
                                }
                                final Date dt = FessFunctions.parseDate(values[0], dateFormat);
                                if (dt != null) {