<Tr> <Td> Kem' </Td> <Td> 1: 44 </Td> <Td> 23: 42 </Td> <Td> 21 h 58 min </Td> </Tr> <Tr> <Td> Reykjavík </Td> <Td> 2: 55 </Td> <Td> 21.6. 2016 0: 03 </Td> <Td> 21 h 08 min </Td> </Tr> <Tr> <Td> Trondheim </Td> <Td> 3: 02 </Td> <Td> 23: 37 </Td> <Td> 20 h 35 min </Td> </Tr> <Tr> <Td> Tórshavn </Td> <Td> 3: 36 </Td> <Td> 23: 21 </Td> <Td> 19 h 45 min </Td> </Tr>

What is the longest day in southern hemisphere