Kārtika (month)
Kārtika (Bengali: কার্তিক Kartik, Bhojpuri: कातिक, Hindi: कार्तिक Kārtika, Odia: କାର୍ତ୍ତିକ Kārttika, Gujarati: કારતક Kārtak, Kannada: ಕಾರ್ತಿಕ , Maithili: कातिक, Marathi: कार्तिक, Nepali: कार्त्तिक, Sanskrit: कार्तिक, Telugu: కార్తీకం,  Tamil: கார்த்திகை) is the eighth month of the Hindu calendar, which falls in October and November of the Gregorian calendar. In India's national civil calendar, Kartika is the eighth month of the year, beginning on 23 October and ending on 21 November. In most Hindu calendars, Kartika begins with the transit of the Sun into Libra, beginning on 18 October and lasting until 15 November. In the Nepali calendar, which is also the country's official calendar, Kartika is the seventh month of the year, similar to the Maithili and Bengali calendars. In Bengal, Kartika marks the start of the dry season (হেমন্ত Hemôntô).
Kārtika (Bengali: কার্তিক Kartik, Bhojpuri: कातिक, Hindi: कार्तिक Kārtika, Odia: କାର୍ତ୍ତିକ Kārttika, Gujarati: કારતક Kārtak, Kannada: ಕಾರ್ತಿಕ , Maithili: कातिक, Marathi: कार्तिक, Nepali: कार्त्तिक, Sanskrit: कार्तिक, Telugu: కార్తీకం,  Tamil: கார்த்திகை) is the eighth month of the Hindu calendar, which falls in October and November of the Gregorian calendar. In India's national civil calendar, Kartika is the eighth month of the year, beginning on 23 October and ending on 21 November. 
In most Hindu calendars, Kartika begins with the transit of the Sun into Libra, beginning on 18 October and lasting until 15 November. In the Nepali calendar, which is also the country's official calendar, Kartika is the seventh month of the year, similar to the Maithili and Bengali calendars. In Bengal, Kartika marks the start of the dry season (হেমন্ত Hemôntô). In the solar Tamil calendar, Kārttikai (கார்த்திகை, /kɑːrt̪iɡəj/) is the eighth month, corresponding to November/December in the Gregorian calendar. It begins when the sun enters the sign of Scorpio. Many festivals, such as Karthikai Deepam, are celebrated in this month.

Etymology
The name of the month is derived from the name of a star, Krittika (Tamil: கார்த்திகை) nakshatra.

Festivals
Several major religious holidays take place in Kartika. These are as follows:

Part of Diwali (amanta tradition): Balipratipada and Govardhan Puja/Annakut (Kartika 1), Bhai Dooj (Kartika 2)
Karthigai Deepam is a lights festival celebrated by Hindu Tamizhans across the world on the Full-Moon Day of the Karthigai Month when the stars align on a Karthika constellation. Tamizhans light Deepams outside and inside their homes to celebrate the birth of Lord Murugan.
Diwali (purnimantatradition), including Govatsa Dwadashi (Kartika 12), Dhanteras (Kartika 13), Naraka Chaturdasi (Kartika 14), Kali Puja and Lakshmi Puja (Kartika 15), Balipratipada and Govardhan Puja/Annakut (Kartika 16), Bhai Dooj (Kartika 17)
Chhath Mahaparv (Kartika 21)
Kartik Poornima (Kartika 15 or Kartika 30)
Sohrai
Kartika Ekadashi (Kartika 11 or Kartika 26)
Nag Nathaiya in Varanasi
Jalaram Jayanti is celebrated mainly in Gujarat on the 7th Shukla Paksha of Kartika.The festival of Kartik Poornima (Kartika 15/30) falls in this month; it celebrated as Dev Deepavali in Varanasi. This coincides with the nirvana of the Jain Tirthankara Mahavira, the birth of the Sikh Guru Nanak, Guru Nanak Jayanti, and the well-known Ayyappan garland festival for the god of Sabarimalai, which is also known as Tripuri Purnima.

The second day of Kartika's bright fortnight is also called Bhaatri Dwitiyaa (similar to Bhai Dooj). It is celebrated by sisters entertaining their brothers, following the legend of Yamuna, who entertained her brother Yama on the same day.Nag Nathaiya in Varanasi, which falls on the fourth Tithi of Kartika's bright fortnight, is an ancient festival celebrating the god Krishna's victory of good over evil. Kashi Naresh (the titular king of Varanasi) would view the festivities from his royal boat.
Every Monday and Ekadashi of this month are special and Abhisheka is offered to Lord Shiva on these oocasions. This month is also considered as the most auspicious month in the Hindu calendar.

See also
Astronomical basis of the Hindu calendar
Hindu units of measurement
Hindu astronomy
Jyotisha

References
External links
Festivals in Karthika masam Archived 2010-01-24 at the Wayback Machine
Kartik Snan - Holy Bathing: A Spiritual Awakening in Hinduism
Kartik Month - thedivineindia.com