Event calendar is the phrase for a product that almost every organisation needs and most of them implement badly. Venues, cities, universities, associations, venues, and communities all maintain one, and the software behind them is a real market.
This name fits a calendar product, an embeddable widget, a listings platform, a local events site, or an API serving event data. The embed business is the interesting one: thousands of sites need a calendar component and would rather rent one than build it, which is a reliable subscription business with low churn.
The .net suits a service or utility of exactly that kind. Nobody types the address of the calendar widget on their local theatre’s website; they encounter it through the product. What the name provides is instant clarity in a search result, a pitch, and a documentation page.
Two plain words, no hyphen, spelled the way everyone spells them.
Offers welcome.