The appearance day of Dhanvantari is celebrated on the 13th day (Trayodashi) of the dark period of the moon in the month of Karttika (October/November).
Dhanvantari is the deified healing art Ayurveda.
Other names of the feast are Dhanteras and Dhanvantari Trayodashi.
To read about Dhanvantari visit
http://keralamythology.blogspot.com/2014/07/legend-of-maruthorvattom-dhanwandhari.html
To read about Dhanteras visit
http://utkarshspeak.blogspot.com/2010/03/dhanteras.html