अग्निर्ज्योतिरहः शुक्लः षण्मासा उत्तरायणम्।तत्र प्रयाता गच्छन्ति ब्रह्म ब्रह्मविदो जनाः ॥

This is the UttaraMarga or Devayana, the northern path or the path of light, by which the Yogis go to Brahman. This path leads to salvation. It takes the devotee to Brahmaloka. The six months of the northern solstice is from the middle of January to the middle of July. It is regarded as the better period for death. There is a vivid description in the Chhandogya Upanishad, the Kaushitaki Upanishad and the Brahma Sutras, chapter IV.3 and 4, ii. 18 and 21.On the road beginning with light (the departed soul proceeds), on account of that being widely known.Having reached the path of the gods he comes to the world of Agni (fire), to the world of Vayu (air), to the world of Varuna (rain), to the world of Indra (king of the gods), to the world of Prajapati (the Creator), to the world of Brahman.They go to the light, from the light to day, from day to the waxing half of the moon, from the waxing half of the moon to the six months when the sun goes to the north, from those months to the year, from the year to the sun.When the person goes away from this world he comes to Vayu (air). Then Vayu room for him like the hole of a wheel and through it he mounts higher. He comes to the sun.From the moon to the lightning there a person that is not human leads him to Brahman.Time is here used in the sense of the path or the stage on the path. Fire and light are the deities who preside over time