Time	The result is shown by the time of day that the event occurred. If you make a report for a full month then the row for the period 08:00 contains all the events that have occurred between 07:30 to 08:00 under all days that month. (If the period is set to 30 minutes, this can also be changed by the users) When using time grouping it is always the end time of the period that is printed. E.g. if a report shows 12:00 and the period is 30 minutes then the row that has the value 12:00 describes the period 11:30 to 12:00.
Date	Each row contains the data for a date e.g. 2014-01-01 Monday.
Week	Each row contains a summary for each year week ex. 2014 W1 contains a summary of all calls that occurred during the 2014 first week This grouping is changed from previous releases. See respectively version of the documentation for a description.
Weekday	Each row contains data for a day of the week e.g. Monday where all data for Mondays in the report is aggregated in this row.
Month	Each row contains data for a month e.g. January where all data that occurred in January month is aggregated.
Quarter	Each row contains a summary for each year quarter as 2014 Q1 contains a summary of all calls that occurred during the 2014 first quarter.
Year	Each row contains all data that occurred in that year.
Year & month	Each row contains data for a month of a particular year e.g. 2014 January. If the report spans multiple years each month will be on its own row.
Period	Each row contains data for the full period.

Note that if you choose to create a report for the period 2014-01-01 to 2014-01-31 and select the year grouping the result will contain a row for 2014, but the values for that row will only contain the calls that have occurred within the report period. This is the same for all the interval groupings.
The same case applies with the period of day. If you create a report that should contain data from 2014-01-01 to 2014-12-31 between 07:00 and 17:00 and group by year the report row saying 2014 will contain calls that has occurred within those hours under that year.

Browser not supported