And so on Tuesday, it is the Communists who will stage a march through Moscow’s streets — the Kremlin has shunted off commemoration of the event into academia, funding a series of conferences and art exhibitions throughout the year.

It is left up to local institutions like museums and city councils, and to Soviet nostalgists, to fill the void. From the village of Filaretovka in Russia’s Far East to Sevastopol in annexed Crimea, messages buried in time capsules are being read out. And in some cases, their authors are there to witness the scene.

Valery Belyayev is one of them. Born in 1941 in a village 40 miles from Cherepovets, Mr. Belyayev grew up desperately poor. He was 2 months old when his father left to fight the Nazis in Stalingrad, in a battle that would claim two million lives.

Throughout the postwar years, Mr. Belyayev watched life in Cherepovets improve, and it was as the 25-year-old deputy head of the city’s Komsomol committee that he helped write the message that was placed in the monolith there back in 1967.

He could not have known then that everything he believed in would fall apart.

“We were convinced that if we could transform our lives at such speed, then of course in 50 years a new era would arrive — we had absolutely no doubt,” Mr. Belyayev said the morning after the message was read aloud to a new generation, as he and other former Komsomol members reminisced, as they often do, inside their community center.

In Cherepovets, a gritty factory town about 300 miles east of St. Petersburg, Komsomol veterans like Mr. Belyayev have their own disco nights, their own clubs and funding from the mayor’s office for events that resurrect a bygone era. For them, the Soviet Union represented a noble idea, and the Komsomol — whose membership reached over 40 million by 1991 — was its social underpinning.