mystery events appear on iphone 5s calendar

the last few weeks events have been appearing on my iphone calendar that I did not create. For example "Krock Trash" meaning I suppose I should take out the trash for Krock. I don't know anyone named Krock, didn't create the event.

I am not sharing my calendars with anyone.

Have you looked at all of the sources for calendars and verified that they are all, in fact, yours? Sometimes, you can add in something like a Google calendar and that will import additional calendar items that you have subscribed to.

Start by looking at the color associated with the event as this will tell you the calendar that it came from.

the color associated with the mystery events is a gray green which is not associated with any of the calendars on my phone

Do you have the option enabled to automatically add items found in Mail?

Settings -> Mail, Contacts, Calendars

All the way at the bottom is an option called "Events Found in Mail"

Events found in mail is off; also the mystery events appearing in the calendar are not in my mail

Open the Calendars app, touch Calendars at the bottom, and look to see exactly what calendars are configured and what their respective colors are.