BACKGROUND: The management and characteristics of ulcerative colitis (UC) have evolved over time. We aimed to clarify how changing clinical profiles and treatment options affect patient outcomes. METHODS: This retrospective multicenter study of 13 hospitals divided diagnostic era into six periods: Era 1 (before June 30, 1998) and five subsequent 5-year intervals, with Era 6 (July 1, 2018-June 30, 2023) representing the most recent period. We compared therapeutic trends and outcomes across diagnostic eras, including the risk of first systemic steroid, advanced therapy (ADT) use, colectomy, UC-associated neoplasia (UCAN), and extracolonic malignancies. RESULTS: We included 1,867 UC patients. The proportion of elderly onset cases was significantly higher in Eras 5-6 (13%) compared to Eras 1-4 (0%-8.1%). Aminosalicylate intolerance was significantly more frequent in Era 6 (10%) and was significantly associated with earlier systemic steroid and ADT use, though not with colectomy or UCAN. While prescribing patterns of conventional therapies remained unchanged, the preferred first-line ADT shifted from infliximab to vedolizumab in recent diagnostic years. The cumulative risk of colectomy and UCAN did not significantly differ between eras. However, the cumulative risk of extracolonic malignancy was significantly higher in recent diagnostic years and significantly associated with older age at diagnosis. CONCLUSIONS: In the recent diagnostic era, the increase in elderly onset UC has been accompanied by a higher malignancy risk, favoring vedolizumab as first-line ADT, especially in elderly patients. Increased aminosalicylate intolerance has led to earlier initiation of systemic steroids and ADTs, which may contribute to improved outcomes.