> Like there is even a downloadable app that you use to plan & book time
If you mean the APT (Astronomer's Proposal Tool) this tool was originally developed for Hubble Space Telescope proposals, and has been in use since at least least 2008[0]. A year or two ago, I found that parts of it are written in Common Lisp[1].
[0] https://www.stsci.edu/scientific-community/software/astronom...
[1] https://apst.stsci.edu/apt/documents/documentation/apt-proje...