kestra-io/kestra · error · PebbleException

The 'dayOfWeek()' function could not parse 'date': {e.getMes

Error message

The 'dayOfWeek()' function could not parse 'date': {e.getMessage()}

What it means

dayOfWeek() parses the date via DateUtils.parseLocalDate and wraps InternalException in a PebbleException. The error means the 'date' argument was supplied but could not be parsed as ISO 8601 (e.g. '01-15-2024', 'Monday', or another non-date string).

Source

Thrown at core/src/main/java/io/kestra/core/runners/pebble/functions/DayOfWeekFunction.java:48

 *
 * @param date any valid ISO 8601 date or datetime string
 */
public class DayOfWeekFunction implements KestraFunction {
    public static final String NAME = "dayOfWeek";

    @Override
    public Object execute(Map<String, Object> args, PebbleTemplate self, EvaluationContext context, int lineNumber) {
        Object dateArg = args.get("date");

        if (dateArg == null) {
            throw new PebbleException(null, "The 'dayOfWeek()' function expects a 'date' argument.", lineNumber, self.getName());
        }

        LocalDate localDate;
        try {
            localDate = DateUtils.parseLocalDate(dateArg.toString());
        } catch (InternalException e) {
            throw new PebbleException(e, "The 'dayOfWeek()' function could not parse 'date': " + e.getMessage(), lineNumber, self.getName());
        }

        return localDate.getDayOfWeek().name();
    }

    @Override
    public List<String> getArgumentNames() {
        return List.of("date");
    }

    @Override
    // HashMap is required here because Map.of() does not allow null values,
    // and null defaults indicate arguments with no meaningful autocompletion default.
    public Map<String, String> getArgumentDefaults() {
        HashMap<String, String> defaults = new HashMap<>();
        defaults.put("date", null);
        return defaults;
    }

View on GitHub (pinned to 823fada927)

Solutions

1. Use ISO 8601 input: 'yyyy-MM-dd' or 'yyyy-MM-dd'T'HH:mm:ss'.
2. Normalize the upstream date to ISO with a transformation before calling dayOfWeek.
3. Validate the string matches an ISO date pattern before use.

Example fix

// before
{{ dayOfWeek('Jan 15, 2024') }}
// after
{{ dayOfWeek('2024-01-15') }}

// Pass an ISO 8601 value
{{ dayOfWeek(date='2024-01-15') }}

// Java: ISO 8601 date pattern check
String iso = "^\\d{4}-\\d{2}-\\d{2}(T\\d{2}:\\d{2}(:\\d{2})?(\\.\\d+)?(Z|[+-]\\d{2}:\\d{2})?)?$";
if (!dateArg.toString().matches(iso)) throw new IllegalArgumentException("date is not ISO 8601");

When it happens

Trigger: Passing a non-ISO or non-date string: {{ dayOfWeek('15/01/2024') }}, {{ dayOfWeek('Monday') }}, or an output field that is text rather than a date.

Common situations: Locale-specific date formats from external systems; binding the wrong (non-date) output field; assuming dayOfWeek accepts any human-readable date.

Related errors

• The 'dayOfMonth()' function could not parse 'date': {e.getMe
• The 'dayOfMonth()' function expects a 'date' argument.
• The 'dayOfWeek()' function expects a 'date' argument.
• The 'hourOfDay()' function could not parse 'date': {e2.getMe
• The 'isDayWeekInMonth()' function could not parse 'date': {e

AI-assisted analysis of kestra-io/kestra@823fada927 (2026-08-14). Data as JSON: /api/errors/c30d6fb35d97d546. Report an issue: GitHub.