Onam Festival is celebrated in the beginning of the first month of Malayalam Calendar (Kolla Varsham) called Chingam. This month corresponds to August-September in Gregorian Calendar and Bhadrapada or Bhadon in Indian (Hindu) Calendar.
The dayof Onam is decided in accordance with the legend of King Mahabali in whose honor Onam is celebrated. People believe that it was this particular day in the month of Chingam when Lord Vishnu took his fifth avatar as Vaamana, appeared in the kingdom of King Mahabali and sent him to nether world.
People believe that it is on the last day, Tiruonam that the spirit of King Maveli visits Kerala, hence the day is marked by feast and festivities. Devotees of Maveli celebrate the golden era witnessed in Maveli's reign during Onam. To welcome their revered ruler, people lay flower mats (Pookalam) in the front courtyard, prepare a grand meal (Onasadya), dance, play and make merry. All this is done to impress upon King Mahabali that his people are prosperous and happy.
