how I get the current time with this chip n what library I used :?: 
I used atmega8535 in my work n I still newbie in micro controller so I need more help to finish my home work.
chip has no built-in date/time clock hardware.
You’d have to connect such, with battery backup, or
implement the chip’s timer for a periodic interrupt. You write code for each interrupt to update the time and date as variables in your program.
You will have to input the starting date/time, by some means - serial port link to a PC, etc.
So your assignment may involve some original work on your part, rather than reusing others’ work.