How to read a panchang

Most Indian households have a panchang somewhere: a fat annual paperback, a temple's folded sheet, or a small grey box on the wall calendar. It looks like a train timetable written half in another language. Almost every number is doing a job.

Start with the fact that loosens the rest. The day here runs from sunrise to the next sunrise. So a line saying something lasts "until 00:17" means a quarter past midnight tonight, and the panchang counts that as today. Because the sun rises at different moments in different places, every sheet names a city. Same sky, different clock.

The word panchang means five limbs: the page is named after five measurements. The tithi is a lunar day, measured as an angle. Each time the moon pulls twelve degrees ahead of the sun, one tithi has passed. Thirty fill a lunar month. The vara is the weekday. The nakshatra is which of twenty-seven patches of sky the moon is in. Yoga and karana are two further counts, mostly for specialists. Yoga is the sun's position added to the moon's, cut into twenty-seven named parts. Karana is half a tithi.

Now the awkward part. The moon hurries and dawdles, so tithis come out unequal, some under twenty hours, some nearly twenty-seven. A tithi will not sit politely inside a date. So there is a rule: the day is named for the tithi running at sunrise. A short tithi can be skipped, and a long one used twice.

That rule is the whole answer to why Hindu festival dates move against the English calendar. Nothing has slipped. You are reading two calendars at once, and one of them keeps time by the moon.

Everything else is a side table arranged around those five. The fortnight says whether the moon is growing or shrinking. The month is named twice, because some regions end it at the new moon and some at the full moon. The year appears two or three times, one count above another, because more than one era is still in use. No table of secrets, only arithmetic.