Based on a Teensy 3.2, this uses GPS to calculate the Hebrew date, and automatically light up laser "candles" on Hanukkah.
The device uses one serial port to get time and location data from the GPS module, one serial port to send text (and music) to the LCD display, and one serial port to drive 54 NeoPixel LEDs. Nine laser diodes are driven by normal digital outputs.
The Teensy and Paul's code libraries made a complicated project (all that calendrical computation, sunrise and sunset time, etc) quite straightforward.
I used a modified version of Paul's TimeLib (changed the tmElements_t structure to use short ints rather than uint_8ts, so I could pass negative values to the makeTime function for doing time math), and Paul's WS2812 LED Display Library.
(The video shows the switch thrown into the "simulation" mode, so it's not live GPS data. Throwing the switch the other way results in it running on real GPS time/location.)