Tasks has 1 day longer

From email:

tasks has 1 day more than indicated.
example: task properties: start 10 august, finish 31 august. But on the drawing the task is finishing on 1st september… even on the lesft panel it is written 31 august…

I can understand that 31 is full day so the next action will start on 1st september. The issue is that if i want to put a milestone at the end, on 31, it will appear on 1st september instead of 31 august

Tasks duration is measured in full business days. They are not 1 day longer. If you need a milestone at the same day when task finishes, connect it with task using Finish-Finish dependency rather than Finish-Start.