Switching from hotmail server to icloud for saving calendar events: please read below:

I have two years of events on my calendar and it is my lifeline. I am thinking of switching the way I save my events because the Hotmail server is not reliable. I will check my phone and all my events for the past two years will vanish. When I spoke to an apple support advisor he told me that some events will not appear as they do now, which makes me nervous because I use the "notes" section in my calendar religiously. Please advise