Using call & ret (but that's maybe not necessary...)
Reducing instruction size

main_loop alignement and size reduction under 32 bytes
Size reduction of _start code

Using smaller operations

For nano sec, sec and min printing

Moved the macro before .data section
Add a .bss section
Reorganisation of .data section

Better comments and op suppression

Writing a proc_nl function to print a newline on a given fd
Enhancement in argument passing to proc_print_time