DATASHEET!!!!

Just as you wouldn't have a clue what CMCON was for a PIC that you never met before, in the same way you need to know what Registers you've got inside your DS1307, in what sequence you arrive at them, and what their contents are.

Download the DATASHEET for the DS1307.

You will follow the SAME proceedure for ANY complex chip (or device) that you come across. Copying and relying on other peoples code is insufficient. It's worse than trying to decypher Egyptian without the Rosetta stone.

And in answer to your question, you can choose to read back whatever you want in whatever sequence you want (though not nescessarilly in one I2C instruction)... the DATASHEET will explain how and reveal other Registers, features and goodies which you may be unaware of, and which the code you are copying from does not take advantage of.