public static System.bool DayInRange( 
   System.DateTime datetime1,
   System.DateTime datetime2,
   System.int daysBefore,
   System.int daysAfter
)

Parameters

datetime1

Checked date.

datetime2

Date that sets the range.

daysBefore

Number of days to the datetime2 date (lower boundary of the range)

daysAfter

Number of days after the datetime2 date (upper boundary of the range)

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference