My suggestion is to add a function that allows to attach data files (e. g. pdf files) to special entries in the calender. For example, if you make an entry in the calender for an upcoming stay in a hotel or flight, it'll be nice if I could attach the pdf file with the booking confirmation. In that case, you have always all information available regarding the booking even though you don't need to enter all data into the system. To make it safe and easier, it might be helpful to limit the formats to pictures, pdfs, doc, etc. What do you think ?