Uttara Phalguni is nakshatra number 12 of the 27 lunar mansions in Vedic astrology, spanning 146.67° of the zodiac in 13°20' steps. Its planetary lord is Sun and its presiding deity is Aryaman.
The Moon's position in Uttara Phalguni at birth shapes the Vimshottari Mahadasha sequence — a Uttara Phalguni birth begins life in the Sun mahadasha, with the balance of that period decided by how far the Moon had travelled through the nakshatra.
Use the free Kundli generator to find whether Uttara Phalguni is your janma nakshatra, and the Panchang to see exactly when the Moon transits Uttara Phalguni on any date.