Classical yoga describes prāṇa — breath-energy — as moving through three main channels: Iḍā on the left, described as lunar, cooling and receptive; Piṅgalā on the right, solar, heating and active; and Suṣumṇā through the centre, said to open only briefly between the two.

Swara Yoga is the practice of tracking which channel is dominant. Its central claim is that the nostril you're breathing through more freely tells you which channel is active, and that this shifts on a schedule anchored to your local sunrise and the lunar day — which is what the Swara calendar in this app calculates for you, locally, from your location.

Western physiology does measure something adjacent: the 'nasal cycle', a well-documented alternation in which nostril is more open, driven by the autonomic nervous system on a cycle of roughly one to four hours. The tradition's tithi-based schedule and the measured nasal cycle are not the same claim, and Delve keeps them clearly separate rather than dressing one up as the other.

What you can do with it, practically: the tradition favours the left (cooling) channel for rest, reflection and sleep, and the right (heating) channel for effort and decisions. The simplest lever is posture — lying on one side opens the opposite nostril within minutes.