Make the UI support entering descriptions better
Because I have to enter a description along with every time, I find this is slow, clumsy and error prone. To understand why from a UX design, probably the best think to do is read up briefly on Fitt's Law.
You've got the gist of that before moving continuing? Great, now you should have an appreciation how fiddly it is to hit a tiny box top right, come down the bottom left for the details, go back to the top right over and over. Most folks probably wouldn't "get" why it's so frustrating, they'd just have the take-away emotion.
I'm not actually in UX myself so I can't offer the ideal solution, but probably something like a table that can be filled out row-by-row, with time and description columns so they're right next to each other. Perhaps with category as a 3rd column, type to complete. And maybe a "add next day" button which extends the table or adds a new table below for each day.