Is It Actually Bad Luck to Start Something Important on a Tuesday?

No, not universally, and this is a good example of a rule that has outgrown its original, narrower meaning. Tuesday, ruled by Mars, is considered unfavourable for a few specific kinds of beginnings, not for everything, and is actually a genuinely good day for other kinds of action entirely.

Tuesday is ruled by Mars in Vedic astrology, and Mars is associated with conflict, aggression and impulsiveness. Over time, through informal, half remembered advice passed down in families, Mars day is a bit intense became flattened into a blanket Tuesday is bad, a real oversimplification of what the tradition actually says.

Mars energy is not inherently negative, it is associated with courage, competition and decisive action. Tuesday is traditionally a reasonably good day for anything requiring boldness or physical energy, starting a fitness routine, having a difficult but necessary confrontation, or beginning something that requires courage more than patience.

The specific traditional caution is mainly around starting a new home or a significant financial commitment on a Tuesday, since Mars's association with conflict is considered a poor match for ventures needing stability and harmony rather than intensity. This is a narrow, specific caution, not a blanket rule against doing anything at all on the day.

The honest answer is that it depends entirely on what you are starting, which is true of most day based rules in Vedic astrology and gets lost every time the nuance is dropped for a shareable, oversimplified warning. A muhurat calculation for a wedding treats Tuesday very differently than one for starting a workout plan.

Rather than treating any single weekday as fixed and universal, real muhurat calculation looks at the full panchang for that specific day, tithi, nakshatra and yoga together, alongside what you are actually trying to start. A Tuesday with a strong nakshatra and a favourable tithi can outperform a safe day with a poor one.