Frequently Asked Questions

NEW iOS 17 issue

• Calendars empty after iOS 17 upgrade

How to add a specific calendar

• Add iCloud calendar
• Add Exchange calendar
• Add Yahoo calendar
• Add GMX calendar
• Add Synology calendar
• Add Nextcloud calendar
• Add ownCloud calendar
• Add CalDAV calendar
• Add Google calendar
• Add Office 365 calendar
• Add Microsoft calendar (Outlook.com, Office 365, Hotmail and Live calendars)
• Add holiday calendar

Other howto's

General

• How to share calendars?
• Enable HTTP communication
• Disable certificate validation

Windows

• How to set OneCalendar on lock screen?
• How to check the current application version?
• How to update to the latest version?

Issues adding and synchronising calendars

• Office 365: Need admin approval
• Synchronization errors with Facebook birthdays
• Appointments entered on phone not visible in OneCalendar
• Error: Only https allowed, allow http in OneCalendar security settings

Android

• Error: An error occured while sending the request

iOS

• Error: The certificate for this server is invalid

macOS

• Error: The SSL connection could not be established

Windows

• Error: The certificate authority is invalid or incorrect
• Error: Could not establish a trust relationship for the SSL/ TLS secure channel...
• Error: A connection with the server could not be established

Other Issues or problems

General

• Appointment spans two days or appointment date/time is wrong (timezone issues)
• The week numbers are incorrect
• Appointments are readonly

Android

• Xiaomi dark mode problems

Windows

• OneCalendar no longer starts
• Appointment reminders don't appear
• OneCalendar is shown in the wrong language
• Missing month while scrolling in month view

Info

• Features of the Premium version
• Contact us
• Feature requests
• What about security?