Hours which are past midnight are suffixed with next day date. In Panchang day starts and ends with sunrise.
Narada Jayanti is celebrated as the birth anniversary of Devrishi Narada Muni. According to Vedic Puranas and mythologies Devrishi Narada is a universal divine messenger and primary source of information among Gods. Narada Muni has the ability to visit all Teen Loks, Akash or Heaven, Prithvi or Earth and Patal or Netherworld and is believed to be first journalist on the Earth. Narada Muni keeps travelling across the universe to communicate the information. However, most of His timely information creates trouble but that is for the betterment of the Universe.
Sage Narada is ardent devotee of Lord Narayana, which is one of the forms of Lord Vishnu. Lord Vishnu in the form of Narayana is considered an embodiment of the truth.
Narada Jayanti is observed on Pratipada Tithi during Krishna Paksha of Jyeshtha month according to North Indian Purnimant calendar. According to South Indian Amavasyant calendar Narada Jayanti falls on PratipadaTithi during Krishna Paksha of Vaishakha month. It is name of Lunar month which differs and in both type of calendars Narada Jayanti falls on the same day.
Usually Narada Jayanti falls next day of Buddha Purnima. Buddha Purnima and Narada Jayanti might fall on same day if Pratipada Tithi is skipped.