The Meaningful Use (MU) reporting period for 2017 is 90 contiguous days for the ten functional measure objectives. The reporting period for Clinical Quality Measures (CQMs) is the full year. This means most eligible professionals (EPs) will not attest until 2018 for 2017.
The only exception is for EPs reporting on the MU measures for the first time, usually the first year after adopt, implement, upgrade (AIU). Those EPs will report any continuous 90-day period for their CQMs. As long as it occurs during 2017, the date range can be the same 90 days as the MU reporting period or a different 90 days.
Best practice is to monitor MU and clinical quality measures through the year. When you find a 90-day period in which the EP meets all functional measures, capture that data in your electronic health record (EHR) or as a dated copy of the dashboard. Then when the year is completed, you will be ready to attest with full-year data on clinical quality measures.