Hours which are past midnight are suffixed with next day date. In Panchang day starts and ends with sunrise.
In Gujarat, Nag Pancham is observed on Krishna Paksha Panchami during Shravan month in Gujarati calendar. Nag Pancham is observed three days before of Krishna Janmashtami. In Gujarati calendar, lunar month starts after Amavasya i.e. with no moon day. Hence as per Purnimanta calendar followed in north Indian states, Nag Pancham in Gujarat is observed during Bhadrapada month.
In most Indian states Nag Pancham is known as Nag Panchami and observed 15 days before of Nag Pancham during Shukla Paksha Panchami in Shravan month.
The day of Nag Pancham is dedicated to Serpent God and people worship snakes as representative of myriad Serpent Gods in Hinduism e.g. Vasuki, Adishesha and Ananta. Devotees keep fasting on Nag Pancham and usually break it after Nag 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.