<Tr> <Td> a = Y mod 4 </Td> <Td> a = 0 </Td> <Td> a = 1 </Td> <Td> a = 2 </Td> <Td> a = 3 </Td> <Td> a = 0 </Td> </Tr> <Tr> <Td> b = Y mod 7 </Td> <Td> b = 6 </Td> <Td> b = 0 </Td> <Td> b = 1 </Td> <Td> b = 2 </Td> <Td> b = 0 </Td> </Tr> <Tr> <Td> c = Y mod 19 </Td> <Td> c = 13 </Td> <Td> c = 14 </Td> <Td> c = 15 </Td> <Td> c = 16 </Td> <Td> c = 2 </Td> </Tr> <Tr> <Td> d = (19c + 15) mod 30 </Td> <Td> d = 22 </Td> <Td> d = 11 </Td> <Td> d = 0 </Td> <Td> d = 19 </Td> <Td> d = 23 </Td> </Tr>

What determines the date for easter every year