Midnight UTC Day Boundary

Western astrology follows civil timekeeping conventions and marks day boundaries at midnight UTC. This aligns with how birth certificates, historical records, and modern databases record time. All natal charts, transit calculations, and progressions are anchored to UTC, with your local birth time converted to UTC using the timezone offset in effect at your birth location. This convention makes charts reproducible globally: a birth recorded in New York on January 1st at 23:00 local time becomes a UTC time on January 2nd, which is how ephemerides and major software store and retrieve positions.

Your chart is timestamped against the same universal clock used by astronomy, aviation, and scientific research. Whether your readings are compared against a transit calendar, another astrologer's chart, or a future TriAstra feature, the underlying moment is the same.