Fullcalendar v6 React date format "DD/MM" instead of "M/d"

I can't find how to change 9am to 09:00, 10am to 10:00

Also can't understand how to change 6/1 to 01/06, 6/2 to 02/06 both in header and in the event. I've found the eventTimeFormat option, but that is all I could achieve: showing the date, time start - time end on the event. Seems I can't change the date to be 01/06 nowhere.

You can fix both issues using dayHeaderFormat and slotLabelFormat.

To display time like 09:00 instead of 9am on the left time axis, use:

slotLabelFormat={{
  hour: "2-digit",
  minute: "2-digit",
  hour12: false
}}

To show the header dates (like 6/1) as 01/06, use:

dayHeaderFormat={{
  day: "2-digit",
  month: "2-digit"
}}

Setting locale="en-GB" in FullCalendar primarily affects how dates and times are formatted. For example, it changes the date format from 06/01 (month/day) to 01/06 (day/month). It also affects how certain built-in text strings are displayed. Full example:

import React from 'react';
import FullCalendar from '@fullcalendar/react';
import timeGridPlugin from '@fullcalendar/timegrid';

export default function MyCalendar() {
  return (
    <FullCalendar
      plugins={[timeGridPlugin]}
      initialView="timeGridWeek"
      allDaySlot={false}
      locale="en-GB"
      events={[
        {
          title: 'test',
          start: '2025-06-01T10:00:00',
          end: '2025-06-01T10:30:00',
        },
      ]}
      eventTimeFormat={{
        day: '2-digit',
        month: '2-digit',
        hour: '2-digit',
        minute: '2-digit',
        hour12: false,
      }}
      dayHeaderFormat={{
        day: '2-digit',
        month: '2-digit',
      }}
      slotLabelFormat={{
        hour: '2-digit',
        minute: '2-digit',
        hour12: false,
      }}
    />
  );
}