Default This my be a dumb.. but spam in the calender...

I recieved a spam messege in the form of an alarm going off and a calender entry on my Galaxy S4's S Planner (I'm running hyperdrive rom). it showed being tied to my gmail account, yet theres absolutely nothing on my gmail account, both mobile and desktop.. I'm guess I'm just curious how this happened and how I can prevent it?

Sent from my SCH-I545 using xda app-developers app
Attached Thumbnails
Click image for larger version

Name:	uploadfromtaptalk1389841288609.jpg
Views:	196
Size:	149.4 KB
ID:	2518783   Click image for larger version

Name:	uploadfromtaptalk1389841312977.jpg
Views:	145
Size:	129.6 KB
ID:	2518784   Click image for larger version

Name:	uploadfromtaptalk1389841324378.jpg
Views:	141
Size:	130.0 KB
ID:	2518785