DECLARE @StartPastDays INT
SET @StartPastDays = 1;

DECLARE @PastDays INT
SET @PastDays = 30;

DECLARE @StartDate NVARCHAR(64)
DECLARE @EndDate NVARCHAR(64)

SET @StartDate = CAST(CONVERT( VARCHAR(10), DATEADD(day, -(@PastDays+@StartPastDays-1), CONVERT(VARCHAR(10),GETDATE(),111)), 111 ) + ' 00:00:00' AS NVARCHAR)
PRINT @StartDate;

SET @EndDate = CAST(CONVERT( VARCHAR(10), DATEADD(day, -@StartPastDays, CONVERT(VARCHAR(10),GETDATE(),111)), 111 ) + ' 23:59:59' AS NVARCHAR)
PRINT @EndDate;

Select Sum(CountSent) AS 'Messages Sent', Sum(CountReceived) AS 'Messages Received'

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