EDIT: found one - Goodtime (thanks user)

Forest is an Android and iOS app (and web addon) that lets you track the amount of time you have spent studying.

I just it to track how much time I've spent studying from month-to-month and from subject-to-subject (through using tags). I don't know that there is an open-source alternative but if there is, that would be amazing. I am about to be finished with college for the summer and so will have time to potentially develop an app if there isn't already one.

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Requirements:

• timer option
• countdown option
• tags (for specific subjects or activities)
• statistics page with weekly, monthly, and annual views

Nice Features to Have:

• study together option
• number of people currently studying