Great Calendar! 1 Question (?)

This is a Great 3rd party Multi-Calendar application. Clean, uncluttered visuals & a friendly user interface kept me from deleting this app., after I opened it for the 1st time. In its current version, it suits my needs more than adequately. I, specifically, love having multiple calendars that can be viewed separately or integrated into one. My question is this: Why cant I use this application off-line? I do not sink this calendar application with my iPhone calendar or any other 3rd party calendar software, nor do I share other calendar info with this calendar app. So, why cant I add calendar events without this app communicating with some server somewhere? Why? Please answer this question!

NIH8U2 about TimeTree: Shared Calendar