Run this script against ReportServer database to obtain basic historical overview of reports execution. Remember that default log history retention is 60 days.
SELECT [EL].[LogEntryId], [EL].[InstanceName], [C].[Path], [C].[Name] [ReportName], [EL].[UserName], CASE([EL].[ReportAction]) WHEN 1 THEN 'Render' WHEN 2 THEN 'BookmarkNavigation' WHEN 3 THEN 'DocumentMapNavigation' WHEN 4 THEN 'DrillThrough' WHEN 5 THEN 'FindString' WHEN 6 THEN 'GetDocumentMap' WHEN 7 THEN 'Toggle' WHEN 8 THEN 'Sort' WHEN 9 THEN 'Execute' ELSE 'Unknown' END [ItemAction], [EL].[TimeStart], YEAR([EL].[TimeStart]) [Start_Year], MONTH([EL].[TimeStart]) [Start_Month], DATENAME(MONTH,[EL].[TimeStart]) [Start_Month_Name], DATENAME(DW,[EL].[TimeStart]) [Start_Day_Of_Week], DATEPART(WEEKDAY,[EL].[TimeStart]) [Start_Day_Number_of_Week], [EL].[TimeEnd], [EL].[TimeDataRetrieval], [EL].[TimeProcessing], [EL].[TimeRendering], CASE([EL].[Source]) WHEN 1 THEN 'Live' WHEN 2 THEN 'Cache' WHEN 3 THEN 'Snapshot' WHEN 4 THEN 'History' WHEN 5 THEN 'AdHoc' WHEN 6 THEN 'Session' WHEN 7 THEN 'Rdce' ELSE 'Unknown' END [Source], [EL].[Status], [EL].[ByteCount],[EL].[RowCount], [EL].[Parameters], [C].[Description], [CBY].[UserName] [CreatedBy], [C].[CreationDate], [MBY].[UserName] [ModifiedBy], [C].[ModifiedDate] FROM [dbo].[ExecutionLogStorage] [EL] LEFT JOIN [dbo].[Catalog] [C] ON [EL].[ReportID] = [C].[ItemID] LEFT JOIN [dbo].[Users] [CBY] ON [C].[CreatedByID] = [CBY].[UserID] LEFT JOIN [dbo].[Users] [MBY] ON [C].[ModifiedByID] = [MBY].[UserID] WHERE [EL].[Source] = 1 AND [C].[Type] = 2 ORDER BY c.[Path], c.[Name] GO