I have sevaral activities using 24 hour calendar. The first activity must start friday afternoon and starting that point it is a 24 hour calendar job (befor ethis it is normal calendar). Because the whole 24 calendar portion will last only 3 days, over a long weekend, it must start on friday afternoon and finish Tuesday morning. (from 8/29 afternoon to 9/2 early morning)

First of all is it possible to show that it starts 8/29 afternoon? and then the first tasks finish saturday afternoon and finish monday morning... then next set of tasks will take another 24 hours. so i must be able to divide the units to hours for that portion I guess, but the rest of the schedule before is in days units as usual. so is this possible?

You may turn on the display of time to show when tasks begin and end. For Project 2007, Tools > Options, General tab.

on MS project 2007 I couldnt see this

Sorry, View tab.