I wanted a Digital Clock for my hostel room so I made one! P.s. I've not focused much on aesthetics.
The main reason behind using a bluetooth module is that I wanted to accomplish the task without an RTC module. Whenever the clock powers on (after a power cut) it goes into the initialization stage in which the bluetooth module turns on and asks for Hours, Minutes and Date. Any android smartphone with a bluetooth terminal can be used to feed this information. The power to HC-05 is automatically cut off after time has been set and control transfers to the time function I've written. Delay function is effectively used to continuously increment seconds. The clock is pretty accurate!
Oh, I also needed a night lamp so I interfaced an LDR and an LED strip. In short, when the tube light turns off, the strip turns on and vice-versa.