pentaho/pentaho-kettle · error · KettleValueException

Can't convert a string to a date

Error message

Can't convert a string to a date

What it means

convertValueToDate() first tries Context.jsToJava(value, Date.class); if that fails it tries to interpret the value as a string and parse it with XMLHandler.stringToDate(). When both attempts fail, it throws KettleValueException('Can't convert a string to a date'). The string form of the JS value is not in the expected date format (XML/ISO yyyy-MM-dd'T'HH:mm:ss.SSS).

Solutions

1. Return a JavaScript Date object (new Date(...)) instead of a string from the script.
2. Parse the string in the script with a known format before assigning it to the Date field.
3. Use the step's field metadata / a Select Values or Calculator step to apply the correct date format mask matching the source string.

Example fix

// before
var orderDate = "31/12/2024"; // cannot be parsed
// after
var parts = orderDate.split("/");
var orderDate = new Date(+parts[2], +parts[1]-1, +parts[0]); // JS Date object

// in the script, before assigning:
var d = new Date(value); // or parse with a fixed format
if (isNaN(d.getTime())) throw new Error("Unparseable date: " + value);

function isDateLike(v) {
  return v instanceof Date || !isNaN(Date.parse(String(v)));
}

try {
  Object date = JavaScriptUtils.convertFromJs(context, value, fieldName, "java.util.Date");
} catch (KettleValueException e) {
  logError("Field " + fieldName + ": value is not a parseable date: " + Context.toString(value));
}

When it happens

Trigger: A BigNumber/Number/Boolean or an arbitrarily formatted string value is routed to a Date output field; the fallback string conversion yields text that XMLHandler.stringToDate cannot parse (e.g. '12/31/2024', 'yesterday').

Common situations: Locale-formatted dates from spreadsheets or CSV ('31-12-2024'); timestamps as epoch millis passed as numbers; users assuming the JS step parses arbitrary date strings.

Related errors

• No data output data type was specified for new field
• Argument of TRUNC of date has to be between 0 and 5
• Argument of TRUNC of date has to be between 0 and 5
• JavaScript conversion to BigNumber not implemented for
• Script.Log.UnexpectedeError

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/4bde7c7df2169ff1. Report an issue: GitHub.

Appendix: source

Thrown at engine/src/main/java/org/pentaho/di/core/util/JavaScriptUtils.java:222

          return null;
        }
      } catch ( Exception e2 ) {
        String string = (String) Context.jsToJava( value, String.class );
        return new BigDecimal( string );
      }
    }
  }

  private static Date convertValueToDate( Object value ) throws KettleValueException {
    try {
      Value v = (Value) Context.jsToJava( value, Value.class );
      return v.getDate();
    } catch ( Exception e2 ) {
      try {
        String string = Context.toString( value );
        return XMLHandler.stringToDate( string );
      } catch ( Exception e3 ) {
        throw new KettleValueException( "Can't convert a string to a date" );
      }
    }
  }
}

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