The first season of The Umbrella Academy ended on a cliffhanger. The Hargreaves kids had decided that the only way to stop the apocalypse was to go back in time and be nice to their sister, Vanya. 

Source: Radio Times

However, it seems that whenever they travelled to, they brought the apocalypse with them, precisely the 23rd of November, 1963.  

Source: Variety

Oh, yeah, that's in the trailer for season 2 of the series, which released yesterday. 

From the looks of the tanks in the trailer and the date of the apocalypse, it would appear that the Cuban Missile Crisis might have some role to play in it. 

Source: Newsweek

You can watch the trailer here: 

The Umbrella Academy returns to Netflix on 31 July 2020.