it depends on what you are asking...

for example here in america we have two different terms\word that get confused for each other but are vastly different and means totally different things...

your word in your post Disassociation is defined as to purposely/ consciously make the decision to stop doing something...

today I disassociated from doing the laundry (in psychological terms in the USA this means I purposely made the decision to stop doing the laundry.

going on that definition and your wording in your post a person would know whether they were..... choosing to ignore and not remember something or whether they experienced a trauma that caused them to not remember something or if they just forgot to do their homework kind of forgetfulness or in your words had a time skip so that they did not remember every detail of what they did.

the other term we have here in america is dissociation (no letter a between two s's)

dissociation here in america having a dissociative reaction (feeling numb, spaced out, foggy minded, disconnected feelings) when encountering a trigger (anything that is extremely emotional for that person.

how do you tell when it goes from not being normal dissociation in my location it becomes a mental disorder when it fits the diagnostic criteria in the link at the bottom of my post which lists all the american dissociative disorders.