Хронология развития UO, даты выхода всех аддонов:
1996 Ultima Online (Alpha version)
1997 Ultima Online
1998 Ultima Online: The Second Age
2000 Ultima Online: Renaissance
2001 Ultima Online: Third Dawn
2002 Ultima Online: Lord Blackthorn’s Revenge
2003 Ultima Online: Age of Shadows
2004 Ultima Online: Samurai Empire
2005 Ultima Online: Mondain’s Legacy
2007 Ultima Online: Kingdom Reborn
2009 Ultima Online: Stygian Abyss
2010 Ultima Online: Adventures On High Seas
2015 Ultima Online: Time of Legends