One day can mean a month in various contexts of federal health reform including the employer fair share requirements, the individual mandate, and required reporting.
For purposes of the employer fair share requirements (4980H), failure to offer coverage for any day can mean failure to offer coverage for that month.
Alternatively, if an employee terminates employment mid-month, and would have been offered coverage for the entire month had they not terminated, coverage is deemed to apply the whole calendar month.
Both of these rules may eventually factor into specific penalty calculations for employer fair share or 4980H.
Also, for purposes of the individual mandate, coverage for one day in the month means coverage for the entire month for purposes of 5000A. See 78 FR 7314. This lessons the chance that someone may be subject to the individual mandate penalty in months where they had partial coverage.
Lastly, for purposes of 6055 and 6056 Reporting, the proposed regulations require coverage reporting by month.
If you need help understanding these rules, please contact Kinney & Larson.