Roop Chaturdashi (Kali Chaudas)
What it is
Roop Chaturdashi, also widely known as Kali Chaudas or Naraka Chaturdashi, falls the day before the main Diwali night. "Roop" means form or beauty, and the day is traditionally associated with an early bath (often before sunrise) using oils and fragrant pastes, and with clearing away the old and unwanted before Diwali proper begins — a day of tidying the body, the home and, symbolically, the year that is ending.
Elsewhere in India this day is linked to the story of Krishna defeating the demon Narakasura and freeing the captives he held, which is why the day also carries the name Naraka Chaturdashi in many regions.
Why we observe it
As a Krishna-leela day it fits naturally into a Pushtimarg calendar: Narakasura's defeat is one more instance of Prabhu setting things right, cleared away the night before the Diwali cluster's most joyous days. The bodily cleansing the day is known for is easy to read as only physical, but it sits in the same place, right before Diwali, that Vagh Baras's tidying does — clearing space again, this time immediately before Diwali night itself.
A Vaishnav can keep Roop Chaturdashi simply: an early start, a proper bath, and a settled mind, arriving at the Diwali cluster's central night already unburdened rather than rushing into it.