​Thank you for your question on CMS871, Hospital Harm - Severe Hyperglycemia. The glucose lab test on 8/28 at 8:00am was done on dayIndex 3, depicted in the table attached. This is determined by the Days In Period logic (see below) which uses the interval of dayPeriod: Interval[startPeriod, endPeriod ). First to note, the interval is looking at 24-hour periods from the start of the encounter to calculate a day. The use of a closed parens ) in the logic indicates that the last minute within the 24-hour interval is excluded. The use of an open bracket [ in the logic indicates the start minute is included within the day interval. Therefore, in your example, each dayPeriod starts at 8:00am and ends at 7:59pm. Days In Period(Period Interval<DateTime>) ( "Interval To Day Numbers"(Period)) DayIndex   let startPeriod: start of Period + ( 24 hours * ( DayIndex - 1 ) ),   endPeriod: if ( hours between startPeriod and     end of Period < 24   ) then startPeriod     else start of Period + ( 24 hours * DayIndex )   return Tuple {     dayIndex: DayIndex,     dayPeriod: Interval[startPeriod, endPeriod )   } Second to note, the glucose lab test on 8/28 at 8:00am will only be considered a hyperglycemic event day (meeting the numerator criteria) if the glucose value is >300 mg/dL.