What’s the hardest part about keeping track of free trials?

I built TrialPing2 to help people avoid surprise charges when free trials or subscriptions renew.

I’m curious: how do you currently keep track of trials and renewals?

Do you use calendar reminders, notes, budgeting apps, or do you usually remember manually?

I’d love to hear what works, what doesn’t, and what kind of reminder system would be most useful.