Most people read a panchang for one line of it. Here is what all five parts measure, and how ZindSa arrives at them without asking a server.
Panchang is pancha plus anga, five limbs. A daily panchang is not one reading; it is five separate measurements of the same moment, and each answers a different question. They are tithi, vaar, nakshatra, yoga and karana. ZindSa computes all five for the day you are looking at, and names each one on the same card.
Four of the five depend on where the Sun and the Moon are. Only vaar, the weekday, does not.
A tithi is the angle between the Moon and the Sun, cut into steps of 12°. The Moon has to gain 12° on the Sun for one tithi to pass, so a lunar month gives 30 of them, Shukla 1 to 15 as the Moon fills, Krishna 1 to 15 as it empties. Because the Moon does not move at a constant rate, a tithi is not a fixed number of hours: it can run short of a day or well over it.
A vaar is simply the weekday, and it is the one ang that needs no astronomy. It is in the list because a great deal of traditional reckoning, rahu kaal, choghadiya, several muhurats, keys off the weekday and nothing else.
A nakshatra is where the Moon sits against the fixed stars, in steps of 13°20′, the zodiac divided by 27. ZindSa reckons this sidereally, so the number it shows is the Moon's position measured from the fixed stars, not from the equinox.
A yoga is the least intuitive of the five. Add the Sun's longitude and the Moon's longitude together, and divide that sum into 27 parts. There are 27 named yogas and they cycle through in order. It is a joint measure of the two bodies rather than a measure of either one.
A karana is half a tithi, a 6° step, so 60 in a lunar month. Sixty slots, but only eleven names: seven movable karanas that repeat eight times through the month, and four fixed ones that appear once each around the new moon. That is why the karana line changes twice as often as the tithi line.
On your phone, from astronomical series, not from a stored almanac table. The Sun uses a truncated VSOP87 series and the Moon a truncated Meeus/ELP series, both public-domain algorithms, with a ΔT correction applied so the series are evaluated on the right time scale. The positions are then converted to nirayana (sidereal) reckoning with the Lahiri ayanamsa. Once you have the Sun and the Moon, all five angs follow arithmetically.
The engine's own stated accuracy is about 0.05° for the Moon and 0.01° for the Sun. Against a 12° tithi step and a 13°20′ nakshatra step that is comfortable, but it is not zero. So when a reading falls within a few minutes of a boundary, ZindSa shows sandhi rather than asserting which side of the line you are on. That the calculation runs entirely on the device is not a promise either: a check in the build pipeline reads the whole calculation layer and fails if any of it reads the system clock, the device locale, or a timezone it was not handed as a parameter.
Three honest limits are worth knowing before you rely on any panchang app, this one included.
The Lahiri ayanamsa here is a linear fit, and the app says so rather than presenting it as exact. Regional traditions genuinely disagree: Tamil and Malayalam panchangs apply a different day-rule at the same astronomical instant, which can shift a date by a day, ZindSa names that divergence on the affected entries instead of quietly picking a side. And several muhurats you will see elsewhere are simply absent here, because their underlying tables could not be verified against a text; a wrong number does not become right by having a caveat attached to it.
Related: how the panchang is computed in the FAQ, and muhurat, choghadiya and rahu kaal, what the difference actually is. All posts.