Now that all the parts are proven to work on the Uno, it was time to move it all over to the 3.3V trinket. The screen and buttons worked perfectly fine, but it turns out that even though the DS1307 RTC works fine with 3.3V on its I2C pins, it still needs 5V input voltage; hooking it up to 3.3V just gives a random date that doesn't change. It doesn't seem like there's a way to get around this, so I've ordered a 5V step-up regulator from Pololu. Hopefully, that'll trick the RTC into behaving properly. While I'm waiting for that to arrive sometime next week, I'll be working on a case to be 3D-Printed, and refining some of the code.