https://captio.co/ (https://twitter.com/EmailYourself) to send quick reminders to myself. It hasn't been updated in a while, e.g. no dark mode, so there might be chance for somebody else to improve. I'd value it at $some USD/month but I might in the minority here. It was a single purchase when I installed it.

My own: https://sunclock.net

Shows sunrise, sunset, and twilight times, and the phase of the moon. For me it connects clock time to the physical world.

Transit app