Jewish communities worldwide face a pivotal question: should the ancient practice of observing two-day festivals be maintained in a modern era where its original calendrical purpose no longer exists? The Conservative movement's Law Committee has proposed eliminating second festival days (except Rosh Hashanah) while inviting Reform Judaism to adopt a second day of Rosh Hashanah for calendar uniformity. Through comparative religious analysis of talmudic sources, halakhic precedents, and denominational practices across Orthodox, Conservative, and Reform Judaism, this investigation reveals that while economic hardship and exile-based arguments for change are largely unconvincing, concerns about rabbinic authority and established minhag (custom) remain significant. Each second day carries distinct religious weight - Simchat Torah, for instance, has developed independent spiritual significance, while other second days may actually diminish their primary observances. More fundamentally, the push for calendar uniformity obscures deeper challenges to Jewish unity, as denominational differences in marriage, divorce, and conversion practices pose greater threats to Jewish continuity than varying festival observances. The research demonstrates that meaningful Jewish unity requires addressing these core issues of personal status and Jewish law rather than focusing solely on coordinating festival schedules.