>A Professor here said that i am obliged to program it... one of us is stupid so who is it?

Have you read the DS1307 Datasheet?

If you haven't then GO DO IT before you ask questions like the one above.

You will discover that when you first Power-Up a DS1307 for the first time (regardless if you have a Battery Backup connected or not), it sits there and DOES NOTHING until you enable it by clearing the CH (Clock Halt) bit in one of it's Registers (which Bit in which Register I leave you to discover by READING the device Datasheet). That Sir is called "programming" - apart from that, how's the chip supposed to know what the current Time and Date is from which to continue timing? Telepathy?

People who can't be bothered to read Datasheets or Manuals and expect everyone else to do their work for them usually get short changed on this forum.