mantinedev/mantine · error · Error

[@mantine/schedule] Invalid end date for event id: ${eventDa

Error message

[@mantine/schedule] Invalid end date for event id: ${eventData.id}

What it means

validateEvent reports that event.end cannot be parsed as a valid date (dayjs(event.end).isValid() === false). Every schedule view validates this before layout. Without a valid end the duration cannot be computed, so the library fails fast.

Source

Thrown at packages/@mantine/schedule/src/utils/validate-event/validate-event.ts:10

import dayjs from 'dayjs';
import { ScheduleEventData } from '../../types';

export function validateEvent(eventData: ScheduleEventData) {
  if (!dayjs(eventData.start).isValid()) {
    throw new Error(`[@mantine/schedule] Invalid start date for event id: ${eventData.id}`);
  }

  if (!dayjs(eventData.end).isValid()) {
    throw new Error(`[@mantine/schedule] Invalid end date for event id: ${eventData.id}`);
  }

  if (dayjs(eventData.end).isBefore(dayjs(eventData.start))) {
    throw new Error(
      `[@mantine/schedule] Event end date is before start date for event id: ${eventData.id}`
    );
  }

  return eventData;
}

View on GitHub (pinned to 8a284e2c2c)

Solutions

Inspect the event with the reported id and fix its end value
Set end equal to start for instantaneous events instead of leaving it empty
Normalise/validate events once at the data boundary before rendering

Example fix

// before
{ id: '1', start: '2025-01-01', end: undefined }

// after
{ id: '1', start: '2025-01-01', end: '2025-01-01' }

Defensive patterns

Strategy: validation

Validate before calling

const safeEvents = events.filter(
  (e) => dayjs(e.start).isValid() && dayjs(e.end).isValid()
);

Type guard

const hasValidDates = (e: ScheduleEventData): boolean =>
  dayjs(e.start).isValid() && dayjs(e.end).isValid();

Prevention

Default end to start for zero-duration events
Reject form submissions with missing dates
Normalise nulls from the API instead of passing them through

When it happens

Trigger: event.end is undefined/null, an empty string, or an unparseable value like '2024-13-45' or 'N/A'. All-day events created without an explicit end are a frequent cause.

Common situations: API omitting end for zero-length events, form where the end-time picker was optional, serialisation turning null into a string 'null'.

Related errors

AI-assisted analysis of mantinedev/mantine@8a284e2c2c (2026-08-28). Data as JSON: /api/errors/303c31d841479d39. Report an issue: GitHub.