That's why it's a ridiculous rule. It's arbitrary and subject to selective enforcement.
But as a guideline you could say if it's after midnight it's probably a party. And if it's not you let people use their judgment, because guidelines are suggestions enforced via social pressure, not via official penalties.
But as a guideline you could say if it's after midnight it's probably a party. And if it's not you let people use their judgment, because guidelines are suggestions enforced via social pressure, not via official penalties.