how accurate does ur birth time actually need to be

three placements, three tolerances

the sun moves about one degree a day. get ur birth date right and the sun's sidereal position is correct to a fraction of a degree, no matter what time u put in. birth time essentially doesn't move it.

the moon moves about thirteen degrees a day, or roughly one degree every two hours. a birth time that's off by an hour can shift the moon's position by half a degree, which is usually fine, unless ur birthday happens to fall right as the moon is crossing into a new rashi. near that boundary, an hour matters. everywhere else, it mostly doesn't.

the rising sign is a different problem entirely. it's not measuring a slow-moving body's position, it's measuring which point of the zodiac was crossing the eastern horizon at that exact minute, and the earth's rotation carries a full sign past that point every two hours. that means the lagna can change roughly one degree every four minutes. a birth certificate that rounds to the nearest fifteen minutes can already be off by three or four degrees, which is enough to matter for house placements even if it doesn't flip the sign itself.

what each level of "off" actually costs u

why the rising sign is this sensitive

the sun and moon's positions are properties of where those bodies actually are in the sky at a given moment, which barely depends on where on earth u're standing. the rising sign is different: it's the intersection of the ecliptic with your specific local horizon, which depends on the exact time and ur exact location, because the earth is rotating u through the sky as u sit there.

that's also why twins born forty minutes apart can, in rarer cases, get different rising signs, while their sun and moon signs are identical. same date, same place, same parents. different exact minute, different point on the horizon.

what actually counts as "accurate enough"

most hospital-recorded birth times in india are accurate to the nearest five to fifteen minutes, which is generally fine for the sun and moon, and good enough for the rising sign unless ur birth falls near a sign or house boundary. the honest failure case isn't small rounding error, it's not having a real birth time at all: a family member's rough memory, "morning sometime," or a guess pulled from a horoscope made decades ago without the actual clock time behind it.

if that's ur situation, don't force a fake precision into a chart. an approximate lagna calculated from a guessed time is not more accurate than admitting u don't have the time and reading the sun and moon placements, which don't need it.

if u don't know your exact time

a few things actually help, in order of usefulness: a birth certificate or hospital discharge summary (often has the recorded time even if the certificate itself doesn't print it), an astrologer's past chart done at the time using a time u or a family member gave then, or, as a last resort, chart rectification, a technique that works backward from major life events to narrow down a likely birth window. rectification is a real technique with real limits: it narrows a window, it doesn't hand u a fake exact minute.

what doesn't help: rounding to the nearest hour "because it's close enough," or picking noon because it's a neutral default. both of those produce a specific, wrong lagna, which is worse than an honest "approximate."

the receipt

the sun's slow daily motion, the moon's roughly thirteen-degrees-a-day motion, and the horizon's rotation-driven roughly one-degree-per-four-minutes motion are all standard orbital mechanics, not Vedic-specific claims. what's Vedic-specific is which of those measurements the tradition builds the most structure on top of: the lagna sets the whole house system, so it's the one placement where precision actually compounds.

Ask Tota computes all three from whatever birth time u give it, using Swiss Ephemeris and Lahiri ayanamsa, and flags when a result is close enough to a boundary that the exact minute matters.