adafruit 0.56 i2c backpack 7 seg display, digital clock. I need a time sketch!

hi everyone, im kinda new to arduino. But have some simple questions. First off, I'm using an arduino uno with adafruit 0.56 7 seg display with i2c backpack. i have the connections correct according to adafruits tutorial. clock to a5/ data to a4 /+ to 5v /- to ground/. but my real question is this. can i use the arduino as a clock and the 7 seg as a display without a real time clock chip? i also have another project with a common cathode single digit 7 seg 10 pin,have it hooked up and i have it as a countdown timer,but i want to use it as a clock...but once again no code or sketch anywhere. I have looked for about 2 weeks every night for about 2 hours a night searching online. Can Someone please help me with this java code sketch before i go insane.... Thanks Ethan