<Table> <Tr> <Th> Date </Th> <Th> Significance </Th> </Tr> <Tr> <Td> April 9 of each year </Td> <Td> Marking Vimy Ridge Day </Td> </Tr> <Tr> <Td> Varies </Td> <Td> The annual memorial service on Parliament Hill to remember deceased parliamentarians </Td> </Tr> </Table> <Tr> <Th> Date </Th> <Th> Significance </Th> </Tr> <Tr> <Td> April 9 of each year </Td> <Td> Marking Vimy Ridge Day </Td> </Tr> <Tr> <Td> Varies </Td> <Td> The annual memorial service on Parliament Hill to remember deceased parliamentarians </Td> </Tr>

Who orders flags to fly at half mast