Datetimegroup is a project mainly written in ..., it's free.
NATO Date Time Group Plasmoid
A plasmoid for those who are (or want to begin) using date time groups (e.g. for NATO or armed forces or fun or whatever reason).
Following things are to do (feel free to add suggestions)
To install just execute install.sh - but you have to execute kbuildsycoca4 and restart plasma-desktop to use it.