I don't suppose you have an oscilloscope you could check the waveforms with? Else, you need to slow down and do one thing at a time. I would suggest you first put the RTC in start mode, and make sure it responds. Your program looks like the sample in the data sheet, except you don't check the status flag. Instead of trying to write, read, then display, start with using a couple of LEDs as Status indicators. Turn one on to show you are operating, then when you check the status flag, if you get an error, then turn it off and turn the second one on. That way, you'll know if your going into start mode was successful, with both your micro setting the start mode, and the RTC responding to it (checking the status register is the only way to know that the RTC responded on the ACK line during the 9th bit time.