Either I'm insane, or my phone is possessed, and that's not a pretty choice!

Wondering how long it was until my holiday, I scrolled down through the weeks on my mobile (cell) phone’s calendar.

Oh look - There’s a reminder for something on Tuesday April 6th! What was that about? I couldn’t remember making any appointments around then.
Opening up the reminder, I was confronted by the following:

14.00: Time to clean my guns.

At first I thought it was simply a prank, and immediately called a couple of likely suspects, who might have thought it funny to mess with my mobile phone, but none were guilty. So what the hell is it all about, and where did this message come from?

Surely the calendar/reminder function is not part of an online network? So nobody could dive in from cyberspace and go fishing with my paranoia.

Somebody had to physically write it in there, but who?
Was it me?
Have I finally driven past the last exit on the Sanity Superhighway?
Am I now reminding myself to do things that I will never need to do?
Is there an evil twin lurking in my head who knows that in fact I actually do have guns, and that they will need cleaning around that time?
Is my phone possessed by the spirit of a Libertarian nutter?

If I do have guns, I’d much prefer to know about them.
Especially if they are dirty and in need of a polish.

Colyoomistas, I am disturbed and confused. Yes, I know there’s nothing particularly newsworthy about either of those revelations, but this little conundrum is upsetting my brainbox, so suggestions of the helpful kind are most welcome.