In Volume I, the protagonist Pip writes about events which took place during his childhood. Pip does not give us the exact dates about the events of his childhood; and the events that he writes about are based on what he can retrieve from his own memory.
One important incident he records is his being hired by Miss Havisham to visit her once a week to entertain her. The first part of Ch. 12 deals with one such visit on a particular day - the very next weekly visit after he had fought with Herbert Pocket. Pip tells us that he is frightened to go to Miss Havisham's house because he might be arrested by the police:
When the day came round for my return to the scene of the deed of violence, my terrors reached their height.
However, nothing of that sort happens and Pip continues his weekly visits to Miss Havisham's house.
In the latter half of the chapter, Pip tells us how he gradually became more and more intimate with Miss Havisham and how she began take an interest in his future:
As we began to be more used to one another, Miss Havisham talked more to me, and asked me such questions as what had I learnt and what was I going to be? I told her I was going to be apprenticed to Joe, I believed.
Pip never tells us how much time elapsed between that one particular visit and the time he began becoming intimate with Miss Havisham.
Finally, one day Miss Havisham asks him to bring Joe along with him so that she can pay him off so that he could be apprenticed to Joe:
We went on in this way for a long time, and it seemed likely that we should continue to go on in this way for a long time, when, one day.
Pip has not maintained a diary and so he is not able to tell us exactly how much time passed from the day he entered Miss Havisham's service till he was apprenticed to Joe.
However, we can guess that approximately Pip would have been in Miss Havisham's service for about six or seven years because usually a boy was apprenticed at the age of fourteen, taking into consideration that Pip would have been about six or seven at the beginning of the novel.
So, we can conclude that in Ch.12 Dickens records one particular day when Pip visited Miss Havisham and that the rest of the chapter telescopes about six or seven years of Pip's life.
Dude, do your own HW. Mr. Courtney will be mad.