"After reading the tutorial i have some idea that i may require 8-Bit Auto Re-Load TMOD timer, so that after 60 seconds it increments again from 1 so that the counting does always starts again after 12:00 clock.."

Do you have a simulator? If you don't, download one. Feel free to download Pinnacle 52 which I wrote myself. You can use the assembler and integrated simulator for free (up to 2k)--but 2k is more than enough to learn about timers. That will let you write short timer programs and try them out and see if they produce the results you are expecting--and if not, it should help you understand what is going on.

Then, learn how a timer works. The timer tutorial explains them and also includes sample code snippets that can help you understand what the tutorial is explaining.

Further, the Real Time Clock tutorial explains how to write a software-based clock. It even includes working code (see step 7). I would think you should definitely review this because it seems to me it's exactly what you're trying to write (?).

If you have doubts about what a given instruction does or how long it takes to execute, check the 8051 instruction set where you will find entries for each and every instruction.

It seems to me all the information you need is here on 8052.com. And there are quite a few other sites out there, some of which have been mentioned in this thread. If you have some question about this, please tell us what it is. I, for one, still don't understand exactly what you are asking or what information you are lacking. Do you understand how the timers (T0, T1, T2) work? If not, what don't you understand? Understanding the timers is the first step in writing a clock, obviously, and very few explanations are going to make sense to you until you have a basic understanding of the timers themselves.

Regards,
Craig Steiner