kestra-io/kestra · error · PebbleException

The 'dayOfMonth()' function could not parse 'date': {e.getMe

Error message

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

What it means

dayOfMonth() delegates parsing to DateUtils.parseLocalDate and wraps any InternalException as a PebbleException. The error means the 'date' argument was present but not parseable as an ISO 8601 date/datetime (e.g. '15/01/2024', 'Jan 15', or a non-date string).

Source

Thrown at core/src/main/java/io/kestra/core/runners/pebble/functions/DayOfMonthFunction.java:38

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

    @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 'dayOfMonth()' function expects a 'date' argument.", lineNumber, self.getName());
        }

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

        return localDate.getDayOfMonth();
    }

    @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. Pass an ISO 8601 value: 'yyyy-MM-dd' or 'yyyy-MM-dd'T'HH:mm:ss'.
2. Reformat the upstream date to ISO before calling dayOfMonth using a script/output transformation.
3. Validate the format before use and fall back to a known good date.

Example fix

// before
{{ dayOfMonth('15/01/2024') }}
// after
{{ dayOfMonth('2024-01-15') }}

// Pebble: normalize to ISO before calling dayOfMonth
{{ dayOfMonth(date=myDate | date(format="yyyy-MM-dd")) }}  // if a date filter is available; otherwise reformat upstream

// 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 locale-specific format like {{ dayOfMonth('15-01-2024') }}, a relative word like 'today', or a value that is a string but not a date (e.g. an id).

Common situations: Upstream system emitting non-ISO dates; user-entered dates in DD/MM/YYYY; binding date to the wrong output field.

Related errors

• The 'dayOfWeek()' function could not parse 'date': {e.getMes
• 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/12390d4d24c47e32. Report an issue: GitHub.