Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: "When a person is observing a voluntary fast, he may break it whenever he wishes."
Hadith Referenceسنن الدارقطني / كتاب الصيام / 2234
Hadith Takhrij«((أخرجه الدارقطني فى سننه برقم: 2231))»