The best open source alternative to Clockify is Kimai, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to Clockify and 16 is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Clockify are Project Hamster (Free, Open Source), Invoice Ninja (Freemium, Open Source), Kapow (Free, Open Source) and Cattr (Free, Open Source).
KTimeTracker helps you track your personal time spent on various tasks and projects. It is useful for tracking billable hours and can report the hours logged by task and day. With KTimeTracker, you can organize a broken-down project as subtasks with unlimited nesting.
TimeTracker helps you record the amount of time you spend on activities; for example, for recording time in a time sheet at work. It provides ways to view, edit, and filter times, and provides a time sheet report as well.