VB.Net Tutorial/Date Time/Date

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Add 3 years to a date

public class Test
   public Shared Sub Main
        Dim Expiration As Date
        Dim NewExpiration As Date
        Expiration = #1/1/2005#
        Expiration.AddYears(3)
        NewExpiration = Expiration.AddYears(3)
        Console.WriteLine("The new expiration date is: " & NewExpiration)
   End Sub
End class
The new expiration date is: 01/01/2008

Add Time to current time

Public Class Tester
    Public Shared Sub Main
        
        Dim rightNow As Date = Now
        Console.WriteLine("RightNow: " & rightNow.ToString)
        " ----- Add time values.
        Console.WriteLine("RightNow.AddHours(5): " & rightNow.AddHours(5))
        Console.WriteLine("RightNow.AddMinutes(6): " & rightNow.AddMinutes(6))
        Console.WriteLine("RightNow.AddSeconds(7): " & rightNow.AddSeconds(7))
        Console.WriteLine("RightNow.AddMilliseconds(8000): " & rightNow.AddMilliseconds(8000))
    End Sub
End Class
RightNow: 11/05/2007 9:09:20 PM
RightNow.AddHours(5): 12/05/2007 2:09:20 AM
RightNow.AddMinutes(6): 11/05/2007 9:15:20 PM
RightNow.AddSeconds(7): 11/05/2007 9:09:27 PM
RightNow.AddMilliseconds(8000): 11/05/2007 9:09:28 PM

Compare Date value in If statement

Module Module1
    Sub Main()
        If (Now.Hour < 12) Then
            Console.WriteLine("Good morning")
        ElseIf (Now.Hour < 18) Then
            Console.WriteLine("Good day")
        Else
            Console.WriteLine("Good evening")
        End If
    End Sub
End Module
Good evening

Date AddYears, AddMonths and AddDays

Public Class Tester
    Public Shared Sub Main
        
        Dim rightNow As Date = Now
        Console.WriteLine("RightNow: " & rightNow.ToString)
        Console.WriteLine("RightNow.AddYears(2): " & rightNow.AddYears(2))
        Console.WriteLine("RightNow.AddMonths(3): " & rightNow.AddMonths(3))
        Console.WriteLine("RightNow.AddDays(4): " & rightNow.AddDays(4))
    End Sub
End Class
RightNow: 11/05/2007 9:09:20 PM
RightNow.AddYears(2): 11/05/2009 9:09:20 PM
RightNow.AddMonths(3): 11/08/2007 9:09:20 PM
RightNow.AddDays(4): 15/05/2007 9:09:20 PM

Date and TimeSpan

public class Test
   public Shared Sub Main
        Dim date1 As Date = #7/20/2004#
        Dim date2 As Date = #8/7/2004#
        Dim elapsed_time As TimeSpan
        elapsed_time = Date.op_Subtraction(date2, date1)
        Console.WriteLine(elapsed_time.Days.ToString)
   End Sub
End class
18

Date.ToOADate

public class Test
   public Shared Sub Main
        Dim D As Date = Now()
        Dim F As Double = D.ToOADate()
        Console.WriteLine(F)
   End Sub
End class
39213.5204361921

Date ToString, ToLongDateString, ToShortDateString, ToLongTimeString, ToShortTimeString and ToUniversalTime

Public Class Tester
    Public Shared Sub Main
        Dim rightNow As Date = Now
        Dim result As New System.Text.StringBuilder
        result.AppendLine("""Now""...")
        result.Append("ToString: ").AppendLine(rightNow.ToString)
        result.Append("ToLongDateString: ")
        result.AppendLine(rightNow.ToLongDateString)
        result.Append("ToShortDateString: ")
        result.AppendLine(rightNow.ToShortDateString)
        result.Append("ToLongTimeString: ")
        result.AppendLine(rightNow.ToLongTimeString)
        result.Append("ToShortTimeString: ")
        result.AppendLine(rightNow.ToShortTimeString)
        result.Append("ToUniversalTime: ")
        result.AppendLine(rightNow.ToUniversalTime)
        result.AppendLine()
        Console.WriteLine(result.ToString)
    End Sub
End Class
Now"...
ToString: 11/05/2007 9:09:26 PM
ToLongDateString: May 11, 2007
ToShortDateString: 11/05/2007
ToLongTimeString: 9:09:26 PM
ToShortTimeString: 9:09 PM
ToUniversalTime: 12/05/2007 4:09:26 AM

dateVariable = #4#

public class Test
   public Shared Sub Main

        Dim dteExpiration As Date
        dteExpiration = #1/1/2004#
        Console.WriteLine(dteExpiration)

   End Sub
End class
01/01/2004 12:00:00 AM

dateVariable = #PM#

public class Test
   public Shared Sub Main

        Dim dteExpiration As Date
        dteExpiration = #8/27/2001 6:29:11 PM#
        Console.WriteLine(dteExpiration)

   End Sub
End class
27/08/2001 6:29:11 PM

dateVariable = "July 2, 2002"

public class Test
   public Shared Sub Main

        Dim dteExpiration As Date
        dteExpiration = "July 2, 2002"
        Console.WriteLine(dteExpiration)

   End Sub
End class
02/07/2002 12:00:00 AM

Dim fourthOfJuly As New Date( 4)

Public Class Tester
    Public Shared Sub Main
        Dim thirdOfJuly As Date = #7/3/1776 11:59:59 PM#
        Dim fourthOfJuly As New Date(1776, 7, 4)
        Dim inTheMorning As New Date(1776, 7, 4, 9, 45, 30)
        Console.WriteLine( _
           "The 3rd and 4th of July, 1776..." & _
           vbNewLine & vbNewLine & _
           "#7/3/1776 11:59:59 PM# ... " & _
           thirdOfJuly.ToString & vbNewLine & _
           "New Date(1776, 7, 4) ... " & _
           fourthOfJuly.ToString & vbNewLine & _
           "New Date(1776, 7, 4, 9, 45, 30) ... " & _
           inTheMorning.ToString)
    End Sub
End Class
The 3rd and 4th of July, 1776...
#7/3/1776 11:59:59 PM# ... 03/07/1776 11:59:59 PM
New Date(1776, 7, 4) ... 04/07/1776 12:00:00 AM
New Date(1776, 7, 4, 9, 45, 30) ... 04/07/1776 9:45:30 AM

Dim inTheMorning As New Date( 30)

Public Class Tester
    Public Shared Sub Main
        Dim thirdOfJuly As Date = #7/3/1776 11:59:59 PM#
        Dim fourthOfJuly As New Date(1776, 7, 4)
        Dim inTheMorning As New Date(1776, 7, 4, 9, 45, 30)
        Console.WriteLine( _
           "The 3rd and 4th of July, 1776..." & _
           vbNewLine & vbNewLine & _
           "#7/3/1776 11:59:59 PM# ... " & _
           thirdOfJuly.ToString & vbNewLine & _
           "New Date(1776, 7, 4) ... " & _
           fourthOfJuly.ToString & vbNewLine & _
           "New Date(1776, 7, 4, 9, 45, 30) ... " & _
           inTheMorning.ToString)
    End Sub
End Class
The 3rd and 4th of July, 1776...
#7/3/1776 11:59:59 PM# ... 03/07/1776 11:59:59 PM
New Date(1776, 7, 4) ... 04/07/1776 12:00:00 AM
New Date(1776, 7, 4, 9, 45, 30) ... 04/07/1776 9:45:30 AM

Dim thirdOfJuly As Date = #PM#

Public Class Tester
    Public Shared Sub Main
        Dim thirdOfJuly As Date = #7/3/1776 11:59:59 PM#
        Dim fourthOfJuly As New Date(1776, 7, 4)
        Dim inTheMorning As New Date(1776, 7, 4, 9, 45, 30)
        Console.WriteLine( _
           "The 3rd and 4th of July, 1776..." & _
           vbNewLine & vbNewLine & _
           "#7/3/1776 11:59:59 PM# ... " & _
           thirdOfJuly.ToString & vbNewLine & _
           "New Date(1776, 7, 4) ... " & _
           fourthOfJuly.ToString & vbNewLine & _
           "New Date(1776, 7, 4, 9, 45, 30) ... " & _
           inTheMorning.ToString)
    End Sub
End Class
The 3rd and 4th of July, 1776...
#7/3/1776 11:59:59 PM# ... 03/07/1776 11:59:59 PM
New Date(1776, 7, 4) ... 04/07/1776 12:00:00 AM
New Date(1776, 7, 4, 9, 45, 30) ... 04/07/1776 9:45:30 AM

Elapsed Ticks

Public Class Tester
    Public Shared Sub Main
        Dim ticksBefore As Long
        Dim ticksAfter As Long
        Dim tickSeconds As Double
        ticksBefore = Now.Ticks
        MsgBox("Press OK to see elapsed seconds")
        ticksAfter = Now.Ticks
        tickSeconds = (ticksAfter - ticksBefore) / 10000000.0
        Console.WriteLine("Elapsed seconds: " & tickSeconds.ToString())
    End Sub
End Class
Elapsed seconds: 0.6875

Get Ticks from DateTime

public class Test
   public Shared Sub Main
    Console.WriteLine("Ticks since 12:00AM January 1, 1 CE="+ Now().Ticks().ToString())
   End Sub
End class
Ticks since 12:00AM January 1, 1 CE=633144834075000000

Moon Phase

Public Class Tester
    Public Shared Sub Main
        Dim phaseDay As Double
        Dim result As String
        phaseDay = MoonPhase(Now.ToUniversalTime)
        result = "UTC is now: " & _
           Now.ToUniversalTime.ToString("u") & vbNewLine & vbNewLine
        If (phaseDay < 0) Then
            result &= "Approx days until new moon: " & _
               (-phaseDay).ToString("F1")
        Else
            result &= "Approx days since new moon: " & _
               phaseDay.ToString("F1")
        End If
        Console.WriteLine(result)
    End Sub
    Public Shared Function MoonPhase(ByVal dateUtc As Date) As Double
        Dim days As Double = dateUtc.Subtract(#1/1/1600#).TotalDays
        Dim cycles As Double = days * 0.03386319 - 12.5
        Return Math.IEEERemainder(cycles, 1.0) * 29.53059
    End Function
End Class
UTC is now: 2007-05-12 04:09:30Z
Approx days until new moon: 4.7

Parse Date: Test an invalid date

Public Class Tester
    Public Shared Sub Main
        Dim testDate As String
        Dim results As New System.Text.StringBuilder
        " ----- Test an invalid date.
        testDate = "Febtember 43, 2007"
        If (IsDate(testDate) = True) Then _
           results.AppendLine(Date.Parse(testDate).ToString)
        Console.WriteLine(results.ToString())
    End Sub
End Class

Select Day Of Week

Module Module1
    Sub Main()
        Dim DayOfWeek As Integer
        DayOfWeek = Now.DayOfWeek
        Select Case DayOfWeek
            Case 1
                Console.WriteLine("Sunday")
            Case 2
                Console.WriteLine("Monday")
            Case 3
                Console.WriteLine("Tuesday")
            Case 4
                Console.WriteLine("Wednesday")
            Case 5
                Console.WriteLine("Thursday")
            Case 6
                Console.WriteLine("Friday")
            Case 7
                Console.WriteLine("Saturday")
        End Select
    End Sub
End Module
Thursday

Subtract Time

Public Class Tester
    Public Shared Sub Main
        Dim results As New System.Text.StringBuilder
        Dim rightNow As Date = Now
        results.AppendLine("RightNow: " & rightNow.ToString)
        results.AppendLine()
        results.AppendLine("One year ago: " & _
           rightNow.AddYears(-1).ToString)
        results.AppendLine("365.25 days ago: " & _
           rightNow.AddDays(-365.25).ToString)
        Console.WriteLine(results.ToString())
    End Sub
End Class
RightNow: 11/05/2007 9:09:36 PM
One year ago: 11/05/2006 9:09:36 PM
365.25 days ago: 11/05/2006 3:09:36 PM

System Time

Public Class Tester
    Public Shared Sub Main
        Dim rightNow As Date = Now
        Dim result As New System.Text.StringBuilder
        result.AppendLine("""Now""...")
        result.AppendLine()
        result.Append("Date: ").AppendLine(rightNow.ToShortDateString)
        result.Append("Time: ").AppendLine(rightNow.ToShortTimeString)
        result.Append("Ticks: ").Append(rightNow.Ticks.ToString)
        Console.WriteLine(result.ToString())

    End Sub
End Class
Now"...
Date: 11/05/2007
Time: 9:09 PM
Ticks: 633145145771093750

ToLongDateString

public class Test
   public Shared Sub Main
        Dim theDate As Date
        theDate = #2/13/1975 3:00:00 AM#
        Console.WriteLine(theDate.ToLongDateString)
   End Sub
End class
February 13, 1975

ToLongTimeString

public class Test
   public Shared Sub Main
        Dim theDate As Date
        theDate = #2/13/1975 3:00:00 AM#
        Console.WriteLine(theDate.ToLongTimeString)
   End Sub
End class
3:00:00 AM
Источник — «http://vbex.ru/index.php?title=VB.Net_Tutorial/Date_Time/Date&oldid=3218»