Andrei Yermash - Konets vechnosti AKA The End of Eternity (1987)

Eternity is an organization and a place which exists outside of time.

It is staffed by humans called "Eternals" capable of traveling “upwhen” and “downwhen” within Eternity and entering the conventional temporal world at almost any point of their choice. Collectively they form a corps of Platonic guardians who carry out carefully calculated and planned strategic minimum actions, called Reality Changes, within the temporal world in order to minimise human suffering as integrated over the whole of (future) human history.

Andrew Harlan, an expert in executing Reality Changes, falls in love with a non-Eternal as he comes to understand his part in a paradoxical scheme to secure the creation of Eternity by sending a young Eternal back in time with the mathematical knowledge to make it

First of all - this rare to find Soviet film stands apart from the many others sci fi movies of that time in the USSR. It deals with the idea, that some real people could get immoratlity by means of controlling the time periods inside the special lab-city called "Vechnost". They look like people but they are trained to work for Vechnost forever, as a part of its mechanism. They correct time holes,help people from other time to solve their problems by means of special mind- operating system.

Everyone from Vechnost is immortal and they live in a very futuristic looking like place in the center of time , but some periods of time blocked from them, so two engineers are sent to solve the problem. Very moody and hypnotic film. I liked it more than "Solaris"

The time-manipulation theme is thought-provoking. Many unpleasant events, such as wars, have led to important scientific advances. For example, the two World Wars led to huge advances in aviation. If the Cold War did not occur, there would not have been a moon-landing as early as 1969. If various wars had been prevented (for example, by preventing Hitler's parents from meeting each other), scientific progress would have been much slower.

The encoded message concerning atomic power is not entirely convincing within the bounds of Asimov’s concept - H. G. Wells could conceive of both atomic power and atomic weapons in The World Set Free (1914), and he was not alone in this. Fermi's work was important, but the lack of it does not explain why no atomic bomb was used - even as demonstration, up to the 30th century (the description of the 24th century includes nuclear energy, which means that the delay in the development, while crucial, was not above 4-5 centuries, or perhaps even affected the mindset of the society instead of the technological progress). This final plot twist does nevertheless signal to the reader what was previously hidden, in “whodunit” fashion -