Most are unproductive, unfocused, and giant wastes of time:

Meetings may be toxic, but calendars are the superfund sites that allow that toxicity to thrive. All calendars suck. And they all suck in the same way. Calendars are a record of interruptions. And quite often they’re a battlefield over who owns whose time.

The article suggests scheduling “productive work time” on your calendar. The other option is to simply cancel all work meetings, as this awesome Ted Talk recommends: