Bhagavad Gita Verse 25, Chapter 8

dhoomo raatristathaa krishnaha shanmaasaa dakshinaayanam |
tatra chaandramasam jyotiryogi praapya nivartate || 25 ||
 
Smoke, night, darkness and the southern movement comprising six months; the yogi (travels through) that path, attains the light of the moon, to return.
 
dhoomaha : smoke
raatrihi : night
tathaa : and
krishnaha : darkness
shanmaasaa : comprising six months
dakshinaayanam : southern movement
tatra : through that path
chaandramasam : of the moon
jyotihi : light
yogi : yogi
praapya : attains
nivartate : return
 
We saw earlier that jeevas who have practised single-pointed devotion travel on the path of light, attain the abode of Lord Brahma, and eventually achieve liberation. Now, Shri Krishna describes the path of the jeeva who has performed good deeds in its lifetime, but had not practiced devotion. This path is called the path of the moon or the lunar path.
 
The jeeva is guided on this path by the deities who preside over the smoke of the pyre, night, the dark lunar fortnight and the six months between summer and winter. Having travelled through the lunar path, these jeevas attain a lower realm called Chandraloka or the abode of the moon. In modern language, this is nothing but heaven. The jeeva enjoys heavenly pleasures, which are the fruits of its earthly actions. Unlike the jeeva in Lord Brahma’s abode, this jeeva returns to earth once the fruits of its good actions have depleted.
 
Both the dark lunar fortnight and the period between summer and winter are relatively less auspicious than their brighter counterparts. But many festivals including Maha Shivraatri and Krishna Janmaashtami are celebrated during the dark lunar fortnight.
 
Shri Krishna summarizes the difference between the two paths in the next shloka.