Welcome to the forum! I'm glad you posted. I hope you find this site to be helpful to you and that perhaps some of the confusion will clear. Feel free to post any questions, thoughts, or rants you have and are comfortable with posting!

And again, welcome.
Most of my alters know what year it is, where they live, etc., but then again that's mainly due to the fact that we share time out in control and are often co-conscious with each other. However, there are 2 alters for sure that are confused about the time, and 1 alter that might not know about the time.
2 of my alters, a 17 yr old named Rebel and a 2 yr old named Lynn, definitely do not share my memories and time-line yet. Rebel still thinks is the summer of 2009, and every time she comes out she's very confused and tries to leave home. My best guess is she's trying to go back to my old apartment I had in 2009. She doesn't know who my current boyfriend is, she doesn't know how to drive, she doesn't know most of her friends aren't our friends anymore, and she doesn't know where she lives. However, she seems to share all of my memories up until summer of 2009.
My 2 yr old, Lynn, doesn't seem to share my memories either, not even my other little alter Cassie's memories. She thinks that we should still be at home with mom and dad, and is confused when she comes out and isn't at home. My boyfriend's been telling her that he's a babysitter, because she'll ask where her mom and dad are. Unfortunately, my mom's dead, so of course that would be a bit difficult to explain to a confused 2 yr old.
The other alter that might not know or care where I/he lives is "Hannibal". I'm sure he knows what year it is, but he doesn't consider himself to be a part of my body/mind, so I have no idea where he thinks he lives (or is supposed to live) or anything. He seems to share my memories, as he knows what happened in my life, but I know he doesn't see them as his own memories, so I have no idea what he makes of the whole situation.
As for bringing them up to date, right now I'm simply waiting for Rebel to be out long enough to process an explanation. It seems every time someone tries to prove something to her, like the fact that it's the year 2011, her face goes blank and she leaves and I come back out. I'm sure that with enough proof, easily understood explanations, time, and patience, I can figure out ways to slowly help her come to terms with the fact that she's 3 years behind. She'll definitely need to be treated gently and given plenty of comfort, so I have plans set up for that as well with trusted people.
With Lynn, she's so young I'm not sure she would be able to fully understand an explanation. And I doubt she could grasp the fact that dad moved away and mom's dead. So for now, I try to distract her from her questions. I offer her safety, love, care, comfort, everything that she could need to feel comfortable. Little kids need to feel safe and loved, and my hope is that with her needs met and people to play with her/look after her like my older alter Rain, she'll feel more at home and will accept the change of environment. It probably won't stop her from asking where mom and dad are, but I'm hoping it'll help her to not focus on the fact that mom and dad aren't here so that she can be happier where she is.
I'm not sure if any of this helped, but at least you know you are not alone in this.

If I think of any more ideas to help bring your child part up to the year 2001, I'll certainly post them here. I wish you the best of luck with this. Remember to be patient and gentle with yourself.