calcom/cal.diy · error · BadRequestException

Invalid start date

Error message

Invalid start date

What it means

A NestJS BadRequestException (HTTP 400) from SlotsService_2024_09_04.reserveSlot. Luxon's DateTime.fromISO(input.slotStart, {zone:'utc'}) produced an invalid DateTime (.isValid === false). The ReserveSlotInput DTO's @IsDateString may accept strings that luxon still rejects, so this is the runtime backstop. The slotStart must be a real instant.

Source

Thrown at apps/api/v2/src/modules/slots/slots-2024-09-04/services/slots.service.ts:121

    if (!eventType) {
      throw new NotFoundException(`Event Type with ID=${input.eventTypeId} not found`);
    }

    if (input.reservationDuration && authUserId) {
      const canSpecifyCustomReservationDuration = await this.canSpecifyCustomReservationDuration(
        authUserId,
        eventType
      );
      if (!canSpecifyCustomReservationDuration) {
        throw new ForbiddenException(
          "authenticated user is not owner of event type, does not have memberships in common with owner of the event type, nor does belong to event type's team or org."
        );
      }
    }

    const startDate = DateTime.fromISO(input.slotStart, { zone: "utc" });
    if (!startDate.isValid) {
      throw new BadRequestException("Invalid start date");
    }

    if (input.slotDuration) {
      this.validateSlotDuration(eventType, input.slotDuration);
    }

    const endDate = startDate.plus({ minutes: input.slotDuration ?? eventType.length });
    if (!endDate.isValid) {
      throw new BadRequestException("Invalid end date");
    }

    const booking = await this.slotsRepository.findActiveOverlappingBooking(
      input.eventTypeId,
      startDate.toJSDate(),
      endDate.toJSDate()
    );

    if (eventType.seatsPerTimeSlot) {

View on GitHub (pinned to 176037d0af)

Solutions

1. Send slotStart as a full ISO 8601 UTC timestamp (new Date().toISOString()), e.g. '2024-09-04T09:00:00.000Z'.
2. Client-side assert DateTime.fromISO(slotStart, {zone:'utc'}).isValid before posting.
3. Use a slot start that was actually returned by GET /v2/slots rather than a hand-built string.
4. Verify the value survives JSON serialization unchanged.

Example fix

// before
fetch('/v2/slots/reserve', { body: JSON.stringify({ eventTypeId, slotStart: '2024-09-04 09:00' }) });

// after
const slotStart = DateTime.fromISO('2024-09-04T09:00:00', { zone:'utc' }).toISO();
if (!slotStart) throw new Error('bad slotStart');
fetch('/v2/slots/reserve', { body: JSON.stringify({ eventTypeId, slotStart }) });

import { DateTime } from 'luxon';

function toValidSlotStart(slotStart: unknown): string {
  if (typeof slotStart !== 'string') throw new TypeError('slotStart must be an ISO string');
  const dt = DateTime.fromISO(slotStart, { zone: 'utc' });
  if (!dt.isValid) throw new RangeError(`Invalid slotStart: ${dt.invalidReason}`);
  return dt.toISO()!;
}
const slotStart = toValidSlotStart(input.slotStart);

function isValidSlotStart(v: unknown): v is string {
  return typeof v === 'string' && DateTime.fromISO(v, { zone: 'utc' }).isValid;
}

try {
  await cal.slots.reserve({ eventTypeId, slotStart });
} catch (e) {
  if (e instanceof HttpError && e.statusCode === 400 && /start date/i.test(e.message)) {
    throw new UserFacingError('Please choose a valid time slot.');
  }
  throw e;
}

When it happens

Trigger: POST /v2/slots/reserve with a slotStart that passes class-validator's date-string check but fails luxon parsing — e.g. a date-only '2024-09-04', an out-of-range component like month 13, or a string with invalid separators.

Common situations: Client sending a date without time; non-UTC offset that luxon disallows; copy-paste truncating the timestamp; passing a number coerced to string.

Related errors

• Invalid end date
• Invalid start date
• Invalid end date
• Could not adjust timezone for slot ${slot.time} with timezon
• Could not adjust timezone for slot end time ${slot.time} wit

AI-assisted analysis of calcom/cal.diy@176037d0af (2026-08-12). Data as JSON: /api/errors/543da94b456933db. Report an issue: GitHub.