Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 6 · Calendar, Muhurta Elements
कालमानं मुहूर्ताङ्गानि च
श्रावणे मास्यमावास्या फाल्गुने मासि पौर्णिमा ।आषाढे कार्तिके मासि ज्येष्ठे चैत्रे च पौर्णिमा ॥ १५१ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 151.
The new moon in Shravana, the full moon in Phalguna. The full moons in Ashadha, Kartika, Jyeshtha and Chaitra.
Simple meaning: More holy days: new moon of Shravana, and full moons of Phalguna, Ashadha, Kartika, Jyeshtha and Chaitra.
मन्वादयो मानवानां श्राद्धेष्वत्यंतपुण्यदा ।
These fourteen days are very good for ancestor rites. A dark 13th in Bhadrapada with Moon in Magha is special.
गजच्छाया तदा ज्ञेया श्राद्धे ह्यत्यंतपुण्यदा ।
That day is Gajachchhaya, very good for ancestor rites. Three moon days on one weekday mean a lost moon day.
तिथिर्वारत्रये त्वेका ह्यधिका द्वे च निंदिते ।
One moon day over three weekdays is an extra moon day. Both the lost and the extra are condemned.