Reduced Test Case

https://codepen.io/miguelTTP/pen/BabpQrp

Do you understand that if a reduced test case is not provided, we will intentionally delay triaging of your ticket?

• I understand

Which connector are you using (React/Angular/etc)?

No connector (vanilla JS)

Bug Description

Bug Description

Problem

When using initialView: 'multiMonthYear' and multiMonthMaxColumns: 2 with three events starting from the same date, where two events last more than 2 days and one event lasts only one day, the calendar fails to display all events when clicking to show all events. The issue is not present when using multiMonthMaxColumns: 1 or selecting the month view, indicating a rendering problem rather than a data issue.

Steps to Reproduce

1. Create a calendar with the following options:

   • initialView: 'multiMonthYear'
   • multiMonthMaxColumns: 2
   • firstDay: '1'
   • timeZone: 'UTC'

2. Add the following events:

   • title: 'Event 1', Start: '2024-01-15', End: '2024-01-20'
   • title: 'Event 2', Start: '2024-01-15', End: '2024-01-20'
   • title: 'Event 3', Start: '2024-01-15'

3. Render the calendar.

Expected Behavior

When clicking to show all events, the calendar should display all three events.

Actual Behavior

The calendar only shows two events.

Additional Information

• FullCalendar Version: 6.1.10
• Screenshots:
  
  

Code Snippet

document.addEventListener('DOMContentLoaded', function() {
  var calendarEl = document.getElementById('calendar');

  var calendar = new FullCalendar.Calendar(calendarEl, {
    timeZone: 'UTC',
    firstDay: '1',
    initialView: 'multiMonthYear',
    multiMonthMaxColumns: 2,
    events: [
      {
        title: 'event 1',
        start: '2024-01-15',
        end: '2024-01-20'
      },
      {
        title: 'event 2',
        start: '2024-01-15',
        end: '2024-01-20'
      },
      {
        title: 'event 3',
        start: '2024-01-15'
      }
    ]
  });

  calendar.render();
});

Thank you in advance for addressing this issue.