Film with countdown announcements such as "Ten minutes to dead time" being broadcast over loudspeakers. 50-70s era.
My recollection of the plot is similar to When Worlds Collide - but I've just watched that and its not it. Maybe I'm mixing the visuals or plot with the audio of two movies. My memory is of blue green planet looming in the sky, while people hurry into a rocket to escape. The countdown is for when the earth will be destroyed. so the rocket must take off before then.