Why does my calendar only show 6 months (or similar) into the future?

The simple reason for limiting calendar length is that without any limit, the calendar file would be infinite in size. That wouldn’t work. The current defaults were selected so that they fill almost all needs, are fast to generate, work with all calendar applications and cause no issues.

Your calendar does not end after 6 or 12 months. Instead, it is updated automatically. So 6 months from now it will still show 6 or 12 months into the future, relative to that point in time. Your calendar will not end (at least not before your subscription period ends). Each calendar is updated every day, or at least every week.

Long time windows can cause multiple issues:

• With longer time periods the file size grows bigger. This causes unnecessary load to the server, the network etc.
• Some clients - most notably Google Calendar and therefore almost all Android phones - refuse to download a calendar if the file is large too big. The limit is currently 1 Mb. If that limit is reached, the calendar download is simply abandoned. There is no error message shown to the user.
• Most importantly, there is practically no benefit in having the calendar show much longer into the future.

If you still want to see further into the future you can do this for most calendars. Please see How do I make my calendar subscription show further into the future? for details.