English translation: night of dispair, darkest hours
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Explanation: In answer to your question as posted.
Moving on to the sentence as expressed, then starting with "Revolutions are not ..." sounds very natural to my English ears.
"Revolutions do not start in the darkness of despair"
However, I do like the suggested "depths of despair" as your original is probably not specifically referring to the time of day but the sombre depths of the particular emotion referred to. Depends ont he rest of your text for tone, register and so on.