When it comes to describing the "good part of the day", there are numerous synonyms that can be used to express this sentiment. Some of the common synonyms for the good part of the day include: the prime, the zenith, the pinnacle, the apex, the summit, the climax, the peak, and the highlight. These words are used to express the most enjoyable and exciting part of the day. Whether it's the time spent with loved ones, the peak productive hours that one enjoys or the moment of sublime achievement that one experiences, the synonyms for the good part of the day are ample enough to convey the joy and satisfaction felt when this happens.