Reading a panchang

Panchang means five limbs. Each is a number derived from where the sun and moon actually are, which is why a panchang is computed rather than merely printed.

The five

• Tithi — the lunar day, one thirtieth of a full cycle of the moon pulling away from the sun. Thirty per lunar month, fifteen waxing and fifteen waning.
• Nakshatra — which of the twenty-seven lunar mansions the moon occupies.
• Yoga — a value from the sun's and moon's positions combined. Twenty-seven of them.
• Karana — half a tithi, so sixty in a cycle across eleven repeating names.
• Vara — the weekday.

The part that causes arguments

The day begins at sunrise, not at midnight. A tithi is named for whichever value holds at sunrise, and it can change partway through the day — a tithi runs anywhere from about 20 to about 27 hours, so it does not align with a calendar day.

This is why two calendars can place the same festival on different dates. If a tithi begins at 4:10 in the afternoon and ends before the next sunrise, one tradition observes it on the first day and another on the second. Neither is wrong; they apply different rules for which sunrise claims the tithi.

Sunrise is also local. A panchang computed for Bengaluru is not correct for Delhi, and neither is correct for Toronto.

What it is used for

Choosing a muhurta — an auspicious window — for anything begun deliberately: a puja, a housewarming, a journey, signing something. The everyday use is smaller: knowing which ekadashi to fast on, and when the festival actually falls this year.