Virus in calandra

I was recently told to go to shorturl website by a trusted source, but later was told that it wasn't working properly. But, before i was told to abort, there was a popup that said "subscribe" and I clicked it and I think it also said to link to calendar. Later in the day, I get events for 2 whole days (today and tomorrow) every hour. Messages such as "you are exposed online, click to fix", "get apple news for free", "viruses alert, check protection now". If I click on the entries, it has url address and nowhere to delete. I tried deleting my history, but no use. Can't find anywhere how to solve this problem. Can anybody help?