The phrase "a certain past" is correct and usable in written English.
It can be used to refer to a specific time or event in the past that is not precisely defined but is understood in context.
Example: "In her stories, she often reflects on a certain past that shaped her character and beliefs."
Alternatives: "a specific past" or "a particular past".
What it means to be human is to exists with a certain past, a personal and cultural history, and by an open series of possibilities that I can seize hold of or not.
They arise when the rate of change of a time-dependent process in its mathematical modeling is not only determined by its present state but also by a certain past state.
The latter is modeled by assuming a fading memory mechanism (e.g., as in [42], [43]) altering the perception of the risk of infection on the basis of the number of cases occurred over a certain (past) period of time.
He involves elderly neighbours in his schemes, several of them only too eager to revert to a more certain past, and he bribes kids to dress as Young Pioneers to serenade his mother on her birthday.
"What could be a problem is if people start nitpicking and making an issue of certain past insider deals.
It said accountant PwC, brought in to take an independent look, deemed certain past accounting policies "not appropriate".
There was a certain point past which people had no idea what I was trying to do.
Driving generally improves by age of the driver, up to a certain point past which our awareness and reaction speed become unreliable.
According to this 'apprehension-content' scheme, retentions – like all forms of perceptual consciousness – are real sensory-like contents in experience, contents that are animated by an act of apprehension, and thus seem a certain degree past.
The speaker has already taken ¬p as established in the common ground, and she further talks about her belief in p at a certain contextually salient past time.
