Gajalakshmi Puja or Gajalaxmi Puja is observed for 11 days starting from Ashwin Purnima or Kumar Purnima (Full Moon day in Ashwin month) in Orissa. In 2018, Gajalakshmi Puja date is October 24.
In some places other than Orissa, Gajalakshmi Puja is also observed on Shukla Paksha Dashami in Bhadrapad month (September). For that regions, Gajalakshmi vrat 2018 date is September 19.
Gajalakshmi Devi is the one who brought back all the wealth lost by Indra. She is also the Goddess of cattle hence is also worshipped during the vratas or pujas dedicated to cattle.