<Tr> <Th> 2012 </Th> <Td> Sun March 11 02: 00 </Td> <Td> Sun November 4 02: 00 </Td> <Td> </Td> </Tr> <Tr> <Th> 2011 </Th> <Td> Sun March 13 02: 00 </Td> <Td> Sun November 6 02: 00 </Td> <Td> </Td> </Tr> <Tr> <Th> </Th> <Td> Sun March 14 02: 00 </Td> <Td> Sun November 7 02: 00 </Td> <Td> </Td> </Tr> <Tr> <Th> 2009 </Th> <Td> Sun March 8 02: 00 </Td> <Td> Sun November 1 02: 00 </Td> <Td> </Td> </Tr>

When did daylight savings start in the united states