<P> The crossover began with Supergirl and Arrow on November 27, 2017, and concluded on The Flash and Legends of Tomorrow on November 28, all on The CW . Arrow, which normally aired on Thursdays at 9 pm, moved to Monday at 9 pm for the crossover and did not air an additional episode on November 30 . Pedowitz stated that they decided to have the crossover occur over two nights, as opposed to the four nights of "Invasion!", because The Flash and Legends of Tomorrow were already paired together on The CW's schedule, and "it would be better and tighter in terms of storytelling to make it like a two - night, four - hour miniseries . We thought this was a tight, concise way of doing it ." Guggenheim added, "We're really approaching this big four - part event as two back - to - back two - hour movies, and I think when you look at it through that lens, it becomes less important for the Supergirl episode to feel like a Supergirl episode and the Arrow episode to feel like an Arrow episode, which was always our approach in the past ." </P> <P> Comic artist Phil Jimenez created a custom cover for the event, which invokes the cover design of the Justice League comic issue #207, the 20th Annual Justice League of America / Justice Society of America crossover . Promotional trailers for the event were released throughout November, before the full trailer was released on November 20 . </P> <Table> <Tr> <Th> Series </Th> <Th> Air date </Th> <Th> Rating / share (18--49) </Th> <Th> Viewers (millions) </Th> <Th> DVR (18--49) </Th> <Th> DVR viewers (millions) </Th> <Th> Total (18--49) </Th> <Th> Total viewers (millions) </Th> </Tr> <Tr> <Td> Supergirl </Td> <Td> November 27, 2017 </Td> <Td> 0.9 / 3 </Td> <Td> 2.71 </Td> <Td> 0.7 </Td> <Td> 1.72 </Td> <Td> 1.6 </Td> <Td> 4.43 </Td> </Tr> <Tr> <Td> Arrow </Td> <Td> November 27, 2017 </Td> <Td> 0.9 / 3 </Td> <Td> 2.52 </Td> <Td> 0.8 </Td> <Td> 1.89 </Td> <Td> 1.7 </Td> <Td> 4.41 </Td> </Tr> <Tr> <Td> The Flash </Td> <Td> November 28, 2017 </Td> <Td> 1.0 / 4 </Td> <Td> 2.82 </Td> <Td> 0.7 </Td> <Td> 1.83 </Td> <Td> 1.7 </Td> <Td> 4.64 </Td> </Tr> <Tr> <Td> Legends of Tomorrow </Td> <Td> November 28, 2017 </Td> <Td> 0.9 / 4 </Td> <Td> 2.80 </Td> <Td> 0.8 </Td> <Td> 1.82 </Td> <Td> 1.7 </Td> <Td> 4.62 </Td> </Tr> </Table> <Tr> <Th> Series </Th> <Th> Air date </Th> <Th> Rating / share (18--49) </Th> <Th> Viewers (millions) </Th> <Th> DVR (18--49) </Th> <Th> DVR viewers (millions) </Th> <Th> Total (18--49) </Th> <Th> Total viewers (millions) </Th> </Tr>

Dc's legends of tomorrow crisis on earth-x part 4