Just wanted to jump in and clarify, as this is actually not correct.
Second by second the AdWords system is working to anticipate how much your ad can show over what is left of the 24 hour day, without exceeding your budget. And then adjusting delivery, second by second.
The system is not primarily looking to see if you have hit your budget so it can then stop. It is actually far more complex that that. And if one's actual budget is less than the recommended amount there is an excellent chance that the ads will not be showing 24/7, even when the budget has not been met.