てのひらカレンダー, also known as てのカレ, is a simple calendar app that allows users to easily check Japanese holidays and traditional six-day cycles. It offers the feature to create lock screen wallpapers by combining your own photos with the calendar. The app's key features include holiday and six-day cycle displays, moon phase and age indication in list format, and the ability to create lock screen wallpapers.

Navigating the calendar is intuitive with swiping gestures for viewing previous and upcoming months or years. Users can also create personalized wallpapers by tapping the "Wallpaper" button, which displays the calendar of the selected month and year as the wallpaper, allowing for customization with personal photos. It's important to note that wallpapers can be saved to the photo library for later use.