What causes "Hour values must be between 0 and 23" in flowable/flowable-engine?

Correct the hour token in the cron string to a value in 0-23 (use 0 for midnight, not 24).

flowable/flowable-engine · error · java.text.ParseException

Hour values must be between 0 and 23

Error message

Hour values must be between 0 and 23

What it means

CronExpression (a Quartz-derived cron parser used by Flowable's ProcessEngineConfiguration clock/timer scheduler) validates each field of the cron expression when the expression is parsed via new CronExpression(String). During storeExpressionVals/addToSet, the HOUR field value (or the end of an hour range) must be in 0-23; otherwise it throws a java.text.ParseException with this message. It is thrown at construction time, before any scheduling happens.

Source

Thrown at modules/flowable-engine-common/src/main/java/org/flowable/common/engine/impl/calendar/CronExpression.java:981

    protected int findNextWhiteSpace(int i, String s) {
        for (; i < s.length() && (s.charAt(i) != ' ' || s.charAt(i) != '\t'); i++) {
        }

        return i;
    }

    protected void addToSet(int val, int end, int incr, int type) throws ParseException {

        TreeSet<Integer> set = getSet(type);

        if (type == SECOND || type == MINUTE) {
            if ((val < 0 || val > 59 || end > 59) && (val != ALL_SPEC_INT)) {
                throw new ParseException("Minute and Second values must be between 0 and 59", -1);
            }
        } else if (type == HOUR) {
            if ((val < 0 || val > 23 || end > 23) && (val != ALL_SPEC_INT)) {
                throw new ParseException("Hour values must be between 0 and 23", -1);
            }
        } else if (type == DAY_OF_MONTH) {
            if ((val < 1 || val > 31 || end > 31) && (val != ALL_SPEC_INT) && (val != NO_SPEC_INT)) {
                throw new ParseException("Day of month values must be between 1 and 31", -1);
            }
        } else if (type == MONTH) {
            if ((val < 1 || val > 12 || end > 12) && (val != ALL_SPEC_INT)) {
                throw new ParseException("Month values must be between 1 and 12", -1);
            }
        } else if (type == DAY_OF_WEEK) {
            if ((val == 0 || val > 7 || end > 7) && (val != ALL_SPEC_INT) && (val != NO_SPEC_INT)) {
                throw new ParseException("Day-of-Week values must be between 1 and 7", -1);
            }
        }

        if ((incr == 0 || incr == -1) && val != ALL_SPEC_INT) {
            if (val != -1) {
                set.add(val);

View on GitHub (pinned to d6d39ce1c6)

Solutions

Correct the hour token in the cron string to a value in 0-23 (use 0 for midnight, not 24).
If the range end exceeds 23 (e.g. 22-25), split or clamp it: ranges that wrap midnight must be expressed as two expressions or with the '*' shorthand.
Validate the cron string before deployment with CronExpression.isValidExpression(cronString) and surface a clear config error to the user.
Wrap construction in try/catch (ParseException) at configuration-load time and fail fast with the offending expression in the log.

Example fix

// before
CronExpression expr = new CronExpression("0 0 24 * * ?"); // throws
// after
CronExpression expr = new CronExpression("0 0 0 * * ?"); // midnight = 0

Defensive patterns

Strategy: validation

Validate before calling

if (!CronExpression.isValidExpression(cron)) {
    throw new IllegalArgumentException("Invalid cron expression: " + cron + " (hours must be 0-23)");
}
CronExpression expr = new CronExpression(cron);

Try / catch

try {
    CronExpression expr = new CronExpression(cron);
} catch (ParseException e) {
    throw new ConfigurationException("Bad hour field in cron: " + cron, e);
}

Prevention

Validate cron strings with CronExpression.isValidExpression() at config load time
Remember midnight is 0, never 24
Use hour abbreviations/ranges only within 0-23
Fail fast at startup, not at first schedule fire

When it happens

Trigger: Calling new CronExpression(cronString) (directly or via CronExpression.getInstance) with an hour token outside 0-23, e.g. '0 0 24 * * ?' or a range whose end exceeds 23 like '0 0 22-25 * * ?'. Only values outside the range and not the '*' ALL_SPEC sentinel trigger it.

Common situations: Hand-written cron strings in BPMN timer definitions or flowable.cfg job configurations; converting from formats that allow 0-24 hours; off-by-one errors like 24 for midnight instead of 0; dynamically generated ranges whose end was computed incorrectly.

Understand the failure class

Background: "value must be between 0 and 1" / "out of range" / "must not be negative" errors: fixing range-validation failures across open-source libraries — this error's family across 42 libraries.

Related errors

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/72bbebda5014c29a. Report an issue: GitHub.