Free and Open Source Software

I currently use TickTick for managing my todo tasks. i haven't been able to find an FOSS replacement for it yet.

The main features that I need in an app like this would be:

1. It should be accessible from the desktop. Don't necessarily need an app, a website is good enough.
2. It should have a decent android app with a home screen widget for listing all the upcoming and overdue tasks.
3. It'll be really nice if it can interpret date and time from the task description to add reminders. For example, writing "Remind me to get some milk at 6pm" will put a reminder for that task at 6PM.

Please let me know if you know about such an app. Thanks.