The calculator is inspired by the old hp67® (registered trademark by Hewlett Packard) calculator. The Legendary 67 app has been developed since 2010. It began as a practice project to get into iOS development. All in all it took about 4 years on and off the project before the first version got released in 2013. Due to time constraints active development ceased to exist until 2019. In 2019, development on version 2.0.0 was started, a complete rewrite of the application from outdated Objective-C into Kotlin and Swift.