The article presents a logical and conceptual interpretation of indefinite pronominal adverbs когда-то, некогда, когда-нибудь, which refer to a different time.?It is noted that the analyzed temporal adverbs are closely connected with the speaking subject, his point of view and the semantics of temporal uncertainty is not alien to them.?It is proved that in the syntactic constructions with the adverb когда-то relevant is the idea to preserve and reproduce in the consciousness of the speaking subject previous events and impressions.The temporal adverb некогда, which is also aiming on the memory is in synonymous relationship with когда-то.?Due to abstract nature of syntactic constructions with когда-нибудь it’s impossible to judge about temporal characteristics of an event, and this reinforces the meaning of temporal unncertainty.

indefinite pronominal adverbs, syntactic time, temporal uncertainty, speaking subject