If matches or events show up twice in your calendar, two sources are almost always active in parallel. The three most common cases:
1. Subscription + old import
You imported an ICS file in the past and later subscribed as well. The imported events remain as a snapshot. Solution: delete the imported (outdated) events or the calendar they were imported into – the subscription stays and keeps updating.
2. The same subscription in two accounts
The calfeed is subscribed once in iCloud and once in your Google account, for example – both accounts show their version on the same device. Solution: check your app's calendar list (iPhone: Calendar → “Calendars”; Google: calendar.google.com on the left). If the calfeed appears twice, remove one of the two subscriptions.
3. Two similar calfeeds
You subscribed to the club calendar and the league calendar, for example – both contain the same matches. Solution: keep the calfeed that suits you better and remove the other. Alternatively, hide one of them.
Android: calovo app
If events are duplicated only within the calovo calendar, use the built-in repair: in the app tap ⋮ at the top right → “Help: calendar not showing?” → “Check and repair”. Right after upgrading to the new app version, events can also appear twice for a while because your old calendars are kept as a backup until you confirm in the app that all events are visible.
Special case: Samsung Calendar
If Samsung Calendar shows events multiple times, the usual cause is the Samsung system calendar “Important contact dates”, which displays the same entries in addition. Solution: hide that system calendar in the Samsung Calendar settings (Manage calendars). This is a display quirk of your calendar app – nothing needs to change about the subscription itself.
The calendar itself appears twice?
If the calfeed is listed twice in your calendar list, it was subscribed twice (often once “locally” and once in iCloud). Remove one of the subscriptions – here is how.