This RTC is I2C compatible you can implement it on 89C51 using bit banging of SCL and SDA lines. U can search for code here in EG itself.
Go thorugh the data sheet of RTC and set the current time parameters at particular addresses mentioned in the data sheet.
For LCD interfacing each row has different command codes so first send ur row command code and then data. In this way U can write any data in any row u want.
LCD interfacing code is also available here in EG.
I also have code for all this but you try by yourself with some reference codes available on net then you will really enjoy the sucesses.
Kaustubh D.