Thirty days and night or two fortnights make a month. Six months make an Ayana.  Ayana is of two kinds — Dakṣināyana (Daksinayana; the southward journey) and Uttarāyana (Uttarayana; the northward journey). Uttarāyana is the daytime for gods, and Dakṣināyana is their night. So, one whole year makes a full day for the gods.