can i use RTC DS1307 with attiny85 I2C

Projects Programming
4

Core so you can program the ATtiny85 the Arduino way...
http://code.google.com/p/arduino-tiny/

I2C library so you can communicate with the RTC...
http://arduino.cc/playground/Code/USIi2c

editing the RTC library from adafruit

I think BroHogan or carl47 has already done something similar. Try searching the forum for their monikers and some keywords.