Repository

Application	FOSS	Actively maintained	Web / Windows / Android / CLI	Simple entry	Remarks
Clockify	❌	✅	✅✅✅❌	✅	Marketed as free, but does have paid plans. Web app seems a little laggy, but it has the fantastic ability to drag to mark time blocks. Android app is clunky with no calendar function.
Toggl Time	❌	✅	✅✅✅❌	✅	Looks very promising. This one is really clean and responsive. Feels more intuitive than clockify, and has generally more long-term users. The project planner on the other hand is not really necessary.
HourStack	❌	✅	✅❌❌❌	❌	Involves pre-planning before executing the schedule. Difficult to see filled blocks of time, and time input is less intuitive.
Super Productivity	✅	✅	✅✅✅❌	❔	Has potential, but looks cluttered (Electron-app). Issue has a lot of bugs and single maintainer since 2017.
Kimai	✅	✅	✅❌❌❌	❌	Offers improvement over basic Excel spreadsheet input. No visualization of time. Looks unnecessarily complex with rate tracking.
ActivityWatch	✅	✅	❌✅✅❌	❔	No syncing. More geared towards indiscriminate data collection, like Rescuetime.
Timewarrior	✅	✅	❌✅❌✅	❔	CLI-only, with a couple desktop GUI wrappers. No sync capabilities.
Timestrap	✅	❌	✅❌❌❌	❔	Promoted by the developer on HackerNews, but remains unstable. Incomplete features.
Timetrap	✅	❌	❌❌❌✅	❔	Rarely updated.
Watson	✅	❌	❌❌❌✅	❔	CLI-only, web GUI not maintained.
Traggo	✅	❌	✅❌❌❌	✅	Only tags, no description of time spent. Very lightly maintained for bug fixes only.
Project Hamster	✅	❌	❌✅❌✅	❔	The hamster died 4 years ago.
gtt	✅	❌	❌✅❌✅	❔	No longer actively maintained in 2021.
Rescuetime	❌	✅	✅✅✅❌	❌	Too much detail with few actionable items, often requires repeated categorization. Not suitable for project-based time tracking.
Google Calendar	❌	✅	✅❌✅❌	❌	Input of individual tasks is very tedious.
Google Sheets	❌	✅	✅❌✅❌	✅	Online-based web interface, often slow to respond and especially difficult to edit on mobile.

This made me realize that not all closed-source software are bad. The potential lock-in is risky, but provided the data being stored is not sensitive, the financial incentive of a company to improve a product often can be a much stronger driving force for development as opposed to free development time by the community.

I eventually selected Toggl Time for its simplicity and ease of use.

Can edit in calendar mode
Relatively stable with minimal lag, fantastic UI
Not particularly suitable for business use (esp. invoicing), but not my use case
Plan on the other hand is a project management tool, hopefully can fulfill with Gantt charts