<Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 13 </Td> <Td_colspan="1"> October 14, 2007 (2007 - 10 - 14) </Td> <Td> February 24, 2008 (2008 - 02 - 24) </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 18 </Td> <Td_colspan="1"> October 5, 2008 (2008 - 10 - 05) </Td> <Td> March 22, 2009 (2009 - 03 - 22) </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 18 </Td> <Td_colspan="1"> October 4, 2009 (2009 - 10 - 04) </Td> <Td> March 28, 2010 (2010 - 03 - 28) </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 18 </Td> <Td_colspan="1"> September 26, 2010 (2010 - 09 - 26) </Td> <Td> March 27, 2011 (2011 - 03 - 27) </Td> </Tr>

When was the first episode of heartland filmed