These are sometimes called memento mori calendars. Memento mori being a Latin phrase that translates to "remember you must die". It's a pretty popular phrase/reminder with the modern day Stoic community.

Remidners of death are often depressing.

It gets me down a little too just because I know I am so weird that I can't understand why anyone would want this.

I actually would have interesting things to put on the timeline. Why anyone would do this though just doesn't make sense to me on any level and I know I am in the minority on that.

I do. But that's also the point of the app. Life is finite!