Change in DC's sleep pattern?

luckymrs.

About a week ago (right before 13 months old) DD started a totally new sleep pattern of not going to bed until between 8:30 and 9pm every night (despite our attempts and "cry it out" experiments to the contrary).  Previous to this, DD had consistently gone to bed between 7 and 7:30pm since she was 6 months old. She still now (as then) sleeps until between 6 and 7am. 

 Did any of you experience a sudden change in DC's sleep pattern like this?  If so, did you find anything successful in coercing DC back to his/her prior sleep pattern?   ;-) 

I know this is wishful thinking, but DH and I really like the hour we (used to) get to ourselves between DD going to bed and us going to bed.