See the CMS text I quoted below. It finalized that doctors are allowed to maximize their scores by cherry-picking their best 90 day periods for each measure and submitting:
Jan-Mar performance numbers for one Quality measure
Jun-Oct performance numbers for a 2nd Quality measure
Jan-Dec for a 3rd
Feb-Jun for a 4th
etc.
The API currently allows a single timeframe for all of Quality, rather than individual timeframes by measure.
This also applies to ACI and IA.
Note that this will likely also apply for 2018 -- they have proposed keeping the 90 day minimum for some categories for yet another year.