What is Udaya Lagna?
The Udaya Lagna is the rising sign — the zodiac sign climbing over the eastern horizon at a given moment, also called the ascendant or simply the lagna. As the Earth turns, the ascendant moves forward through all twelve signs in a day, so at any time of day a specific rashi is "rising". The table above shows, for your location and date, the exact stretch during which each sign holds the ascendant.
Why the Lagna matters
The lagna is the anchor of every muhurat chart. When a time is chosen for an important act — a marriage, griha pravesh, a business start — the sign rising at that moment (lagna shuddhi) should be strong and unafflicted, and often a sign friendly to the act is preferred. Fixed signs suit lasting matters, movable signs suit travel and quick work, and dual signs suit flexible or repeated activity.
How the rising sign changes through the day
Each sign is on the ascendant for roughly two hours, but the exact length varies with your latitude and with the sign itself — some signs rise quickly (short ascension) and others slowly (long ascension), so the durations in the table are uneven. Because it depends on both latitude and longitude, the lagna timings differ from city to city; set your location above.
Using the Lagna table
Read it together with the day's Panchang (tithi and nakshatra), the Choghadiya and Hora for the quality of the hour, and keep the choice clear of Rahu Kaal.