Hours which are past midnight are suffixed with next day date. In Panchang day starts and ends with sunrise.
Nagula Chavithi is observed on the fourth day after Deepavali Amavasya during Karthika masam. Nagula Chavithi is a festival to worship Nag Devatas (Serpent Gods) which is mainly observed by married women for the wellbeing of their children.
Nagula Chavithi is a major festival in Andhra Pradesh and some parts of Karnataka.
It is believed that any Puja offered to snakes would reach to the serpent Gods. Hence people worship live snakes on the day as representative of serpents Gods who are revered and worshipped in Hinduism. Although there are several serpent Gods, following twelve are worshipped during Nagula Chavithi Puja -
सर्वे नागाः प्रीयन्तां मे ये केचित् पृथ्वीतले।
ये च हेलिमरीचिस्था येऽन्तरे दिवि संस्थिताः॥
ये नदीषु महानागा ये सरस्वतिगामिनः।
ये च वापीतडगेषु तेषु सर्वेषु वै नमः॥
Mantra Translation - May the snakes who are staying in this world, sky, heaven, sun-rays, lakes, wells, ponds etc. bless us and we all salute them.
अनन्तं वासुकिं शेषं पद्मनाभं च कम्बलम्।
शङ्ख पालं धृतराष्ट्रं तक्षकं कालियं तथा॥
एतानि नव नामानि नागानां च महात्मनाम्।
सायङ्काले पठेन्नित्यं प्रातःकाले विशेषतः।
तस्य विषभयं नास्ति सर्वत्र विजयी भवेत्॥
Mantra Translation - The names of nine Nag Devtas are Ananta, Vasuki, Shesha, Padmanabha, Kambala, Shankhapala, Dhritarashtra, Takshaka and Kaliya. If chanted regularly every day in the morning, will keep you protected from all evils and make you victorious in life.