Three conditions a Vedic chart is commonly checked for: Mangal dosha, from where Mars sits; Kaal Sarpa, from whether every planet lies to one side of the Rahu–Ketu axis; and Sade Sati, from where Saturn is transiting relative to your Moon right now. Each is stated with the rule that produced it.
Birth time is needed here: the Lagna (ascendant) changes sign every two hours, and Mangal dosha is counted from it. Without an accurate time the result from the Lagna is unreliable; the Moon-based result is not.
Mangal dosha is present when Mars occupies the 1st, 2nd, 4th, 7th, 8th or 12th house counted from the Lagna, from the Moon, or from Venus. Many traditions treat Mars in its own sign (Mesha or Vrishchika) or exalted in Makara as softening the dosha; those cases are noted, not silently removed. Kaal Sarpa is present when all seven other grahas fall within the half of the zodiac from Rahu to Ketu (anuloma) or from Ketu to Rahu (viloma). Sade Sati is the seven-and-a-half years during which Saturn transits the sign before your Moon, your Moon sign, and the sign after; it is checked against today's Saturn.
Houses are whole-sign (each house is one full rashi), which is what these classical rules assume. Rahu and Ketu are at the mean node. A dosha is a description of a chart, not a sentence: what it means for you, and what if anything to do about it, is a reading, and this page does not pretend to be one.
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