To be future proof, neutriNote or Orgzly store notes in plain text format. Orgzly is open source as well.
neutriNote handles long text very well even on my budget backup phone. Its search function is quite reminiscent that of a basic unix based editor. Definitely have a look at this app.
Not sure what reverse calendar means, do check out neutriNote, timestamp, tag support, and search. Sounds like something you are looking for.