If you are planning to include RTC in to your project, probably the best way is to use ready made modules that come with RTC IC, crystal and backup battery. In fact these modules once powered do work stand alone. IT is like a small clock that can be connected anywhere. One thing may be tricky – setting correct time and other configurations. The only way is to connect to it using I2C or SPI interface.
To make things easier, Luca brought special tools for this. He made a GUI for PC and Arduino sketch. All you need to upload Arduion sketch and connect to PC. Then run PC program. After all is set-up, you can attach RTC module to Arduino using I2C interface and start configuring it. Practically Arduino accepts simple commands through serial interface. So any terminal software would work too. But GUI makes things much simpler and faster. Here you can set time and date by picking right values and uploading to Arduino. Once set-up is done, you can disconnect RTC module and use elsewhere.