Shri Phadnis writes…
“There is no such thing as a Solar Month in indian calendars. Can Shri. Oak state the names and days of all 12 months and when the first month begins?”
Taittiriya Samhita (Yajurveda) does talk of 12 solar months of Indian calendar.
Chaturtha Kanda – Chaturtha Prapathak – 11 (Taittiriya Samhita 4:4:11) states…
a (Ye are) Madha and Madhava, the months of spring.
b (Ye are) Çukra and Çuci, the months of summer.
c (Ye are) Nabha and Nabhasya, the months of rain.
d (Ye are) Isa and Urja, the months of autumn.
e (Ye are) Saha and Sahasya, the months of winter.
f (Ye are) Tapa and Tapasya, the months of the cool season.
The text does not tell us either the beginning of the year or the duration of each month in days.