Time Tracking Software

Titra – self hosted minimalistic time tracking which can work as add-on for the Wekan kanban board software
Kanboard Time Tracking Editor – add-on for kanban board software Kanboard
Traggo – Golang-powered tag-based time tracking tool. No tasks, only tagged time spans.
Kimai – project-based self hosted time tracking tool
Procrastitracker (Github) – Windows only. Track programs you opened and the time you spent inside of them. Also tracks which sites you visited for some web browsers.

Watson (Python)
Timetrap (Ruby)
Taskwarrior
arbtt – automatic, rule-based time tracker for Linux (tracks time you spent inside X11 applications)

CLI