You likely have the information you need on this by now, but you posed a good question that is worth answering nonetheless. Sorry this was not answered in a timely manner, it must have fallen through the cracks!
Since this question was asked, ATUS samples through 2012 have been added to AHTUS. To link more recent ATUS samples to the AHTUS, you will need to combine the two datasets in terms of weights which requires a set of transformations to be comparable. Syntax used by the Centre for Time Use Research (CTUR) to harmonize ATUS data into AHTUS format is available here. For a more detailed discussion on harmonizing ATUS with AHTUS, see this forum post. You might also consider using MTUS, which is harmonized for comparability with international time diary data and has incorporated both ATUS and AHTUS. It would allow you to do a cross-time analysis and provides a weight (PROPWT) that is comparable across time.