<Tr> <Th> DST began </Th> <Td> Mar 12, 2017 </Td> </Tr> <Tr> <Th> DST ends </Th> <Td> Nov 5, 2017 </Td> </Tr> <P> The Eastern Time Zone (ET) is a time zone encompassing 17 U.S. states in the eastern part of the contiguous United States, parts of eastern Canada, the state of Quintana Roo in Mexico, Panama in Central America, and the Caribbean Islands . </P> <P> Places that use Eastern Standard Time (EST) when observing standard time (autumn / winter) are 5 hours behind Coordinated Universal Time (UTC − 05: 00). </P>

What is the western border of the eastern time zone