Hindu Calendar has undergone many changes since its inception. Many of these changes have been to regionalize the calendar. At present there are two main calendars that are followed in Hinduism:
Shaka Samvat (Saka Samvat or Shalivahana era): is the most commonly used Hindu Calendar and is the Indian National Calendar for festivals. This calendar was established by The Satavahana king Shalivahana (sometimes identified as Gautamiputra Satakarni). This calendar is followed in South India and Maharashtra. This is also the Cambodian Budhist Calendar.
Bikrami Samvat (Vikram Samvat or Vikrami Samvat): This was estabished by Indian Empror Vikramaditya . It is the official calendar of Bangladesh and Nepal and is widely followed in Western and Norther India.
Both of these calendars are Lunisolar Calendars with 12 months. Each month is divided in to two pakshas (phases): Shukla (bright half) and Bahula (dark half).
Hindu Calendar Months
There are twelve lunar month in Hindu Calendar
6. Bhaadra or, Bhādrapad
9. Agrahayana or, Mārgashīrsha