I love the Jesus Calling books and have had the app for about a year. This year, however, there is a bug that prevents you from finishing reading today's devotional before going to the previous date. In other words, as you try to read April 30, the screen switches to April 29 after 2 seconds, and then April 28. I have reported the bug three times, and each time I get an automated email saying that they are aware and it will be fixed in a few days.
It has been about two months and the bug is still not fixed. I am very disappointed in the lack of response from their technical team.