Calculating DateTime Difference or interval
Suppose that you have two date time values one is startdate and second is EndDate, and you want to calculate time interval between both dates ,in this situation we can use timespan object like this:
(According to MSDN: A TimeSpan object represents a time interval (duration of time or elapsed time) that is measured as a positive or negative number of days, hours, minutes, seconds, and fractions of a second. The TimeSpan structure can also be used to represent the time of day, but only if the time is unrelated to a particular date. Otherwise, the DateTime or DateTimeOffset structure should be used instead.)
Dim StartTime As DateTime = #6/12/2008 3:09:00 PM#
Dim EndTime As DateTime = #6/10/2008 12:04:00 PM#
Dim TimeDiff As TimeSpan = EndTime - StartTime
Dim Days As Integer = TimeDiff.Days 'calculate Value of Days Component
Dim Minutes As Integer = TimeDiff.Minutes 'calculate Value of Minutes Component
Dim Seconds As Integer = TimeDiff.Seconds 'calculate Value of Seconds Component
Dim TotalDays As Integer = TimeDiff.TotalDays 'calculate Value of Total Days
Dim TotalHours As Integer = TimeDiff.TotalHours 'calculate Value of Total Minutes
Dim TotalSeconds As Integer = TimeDiff.TotalSeconds 'calculate Value of Total Seconds
we can use subtrat method for calculating difference between two date like :
TimeDiff = EndTime.Subtract(StartTime)
Add a day, a month and a year to a Date
Dim FirstDate As Date
Dim SecondDate As Date
FirstDate = #2/28/2010#
'Add a day
SecondDate = FirstDate.AddDays(1)
'Add some months
SecondDate = FirstDate.AddMonths(6)
'Subtract a year
SecondDate = FirstDate.AddYears(-1)