Source: Ausiello Files [http://ausiellofiles.ew.com/2010/04/19/season-finale-dates-confirmed/]

(__ABC__)

• Desperate Housewives: May 16
• Grey's Anatomy: May 20
• LOST: May 23 [Series Finale; 2 1/2 hours]
• Modern Family: May 19

(__CBS__)

• Big Bang Theory: May 24
• Criminal Minds: May 26
• CSI: NY: May 26
• How I Met Your Mother: May 24
• Medium: May 21
• The Mentalist: May 20

(__CW__)

• Supernatural: May 13
• Smallville: May 14

(__FOX__)

• Bones: May 20
• Fringe: May 20
• House: May 17

(__NBC__)

• Community: May 20
• The Office: May 20
• Parks and Recreation: May 20