This app uses the calendar function of iOS. With this calendar setting, schedules older than one month are automatically saved in iCloud and disappear.
In order to display these past events, please change the settings as below.
1. Open the iOS Settings app.
2. Tap "Calendar".
3. Tap "Synchronize".
4. Tap "All Events".
It's all.
When you open this app, all the events are displayed.