Dim date1 As Date = Date.Now
Dim date2 As Date = Date.UtcNow
Dim date3 As Date = Date.Today

Dim dateString As String = "5/1/2008 8:30:52 AM"
Dim date1 As Date = Date.Parse(dateString,
                       System.Globalization.CultureInfo.InvariantCulture)
Dim iso8601String As String = "20080501T08:30:52Z"
Dim dateISO8602 As Date = DateTime.ParseExact(iso8601String, "yyyyMMddTHH:mm:ssZ",
                              System.Globalization.CultureInfo.InvariantCulture)
Console.WriteLine(dateISO8602)

Dim date1 As Date = #3/1/2008 7:00AM#
Console.WriteLine(date1.ToString())
' For en-US culture, displays 3/1/2008 7:00:00 AM

Dim date1 As Date = #3/1/2008 7:00AM#
Console.WriteLine(date1.ToString("F"))
' Displays Saturday, March 01, 2008 7:00:00 AM

Dim formats() As String = {"yyyyMMdd", "HHmmss"}
Dim dateStrings() As String = {"20130816", "20131608",
                              "  20130816   ", "115216",
                              "521116", "  115216  "}
Dim parsedDate As DateTime

For Each dateString As String In dateStrings
    If DateTime.TryParseExact(dateString, formats, Nothing,
                           DateTimeStyles.AllowWhiteSpaces Or
                           DateTimeStyles.AdjustToUniversal,
                           parsedDate) Then
        Console.WriteLine($"{dateString} --> {parsedDate:g}")
    Else
        Console.WriteLine($"Cannot convert {dateString}")
    End If
Next

Dim thTH As New CultureInfo("th-TH")
Dim value As New DateTime(2016, 5, 28)

Console.WriteLine(value.ToString(thTH))

thTH.DateTimeFormat.Calendar = New GregorianCalendar()
Console.WriteLine(value.ToString(thTH))

Private Sub ThaiBuddhistEraParse()
    Dim thTH As New CultureInfo("th-TH")
    Dim value As DateTime = DateTime.Parse("28/5/2559", thTH)
    Console.WriteLine(value.ToString(thTH))

    thTH.DateTimeFormat.Calendar = New GregorianCalendar()
    Console.WriteLine(value.ToString(thTH))
    ' The example displays the following output:
    '       28/5/2559 0:00:00
    '       28/5/2016 0:00:00
End Sub

Dim thTH As New CultureInfo("th-TH")
Dim dat As New DateTime(2559, 5, 28, thTH.DateTimeFormat.Calendar)
Console.WriteLine($"Thai Buddhist Era date: {dat.ToString("d", thTH)}")
Console.WriteLine($"Gregorian date:   {dat:d}")

Dim thTH As New CultureInfo("th-TH")
Dim cal As Calendar = thTH.DateTimeFormat.Calendar
Dim dat As New DateTime(2559, 5, 28, cal)
Console.WriteLine("Using the Thai Buddhist Era calendar:")
Console.WriteLine($"Date: {dat.ToString("d", thTH)}")
Console.WriteLine($"Year: {cal.GetYear(dat)}")
Console.WriteLine($"Leap year: {cal.IsLeapYear(cal.GetYear(dat))}")
Console.WriteLine()

Console.WriteLine("Using the Gregorian calendar:")
Console.WriteLine($"Date: {dat:d}")
Console.WriteLine($"Year: {dat.Year}")
Console.WriteLine($"Leap year: {DateTime.IsLeapYear(dat.Year)}")

Dim thTH As New CultureInfo("th-TH")
Dim thCalendar As Calendar = thTH.DateTimeFormat.Calendar
Dim dat As New DateTime(1395, 8, 18, thCalendar)
Console.WriteLine("Using the Thai Buddhist Era calendar:")
Console.WriteLine($"Date: {dat.ToString("d", thTH)}")
Console.WriteLine($"Day of Week: {thCalendar.GetDayOfWeek(dat)}")
Console.WriteLine($"Week of year: {thCalendar.GetWeekOfYear(dat, CalendarWeekRule.FirstDay, DayOfWeek.Sunday)}")
Console.WriteLine()

Dim greg As Calendar = New GregorianCalendar()
Console.WriteLine("Using the Gregorian calendar:")
Console.WriteLine($"Date: {dat:d}")
Console.WriteLine($"Day of Week: {dat.DayOfWeek}")
Console.WriteLine($"Week of year: {greg.GetWeekOfYear(dat, CalendarWeekRule.FirstDay, DayOfWeek.Sunday)}")

Public Sub PersistAsLocalStrings()
    SaveDatesAsStrings()
    RestoreDatesAsStrings()
End Sub

Private Sub SaveDatesAsStrings()
    Dim dates As Date() = {#6/14/2014 6:32AM#, #7/10/2014 11:49PM#,
                          #1/10/2015 1:16AM#, #12/20/2014 9:45PM#,
                          #6/2/2014 3:14PM#}
    Dim output As String = Nothing

    Console.WriteLine($"Current Time Zone: {TimeZoneInfo.Local.DisplayName}")
    Console.WriteLine($"The dates on an {Thread.CurrentThread.CurrentCulture.Name} system:")
    For ctr As Integer = 0 To dates.Length - 1
        Console.WriteLine(dates(ctr).ToString("f"))
        output += dates(ctr).ToString() + If(ctr <> dates.Length - 1, "|", "")
    Next
    Dim sw As New StreamWriter(filenameTxt)
    sw.Write(output)
    sw.Close()
    Console.WriteLine("Saved dates...")
End Sub

Private Sub RestoreDatesAsStrings()
    TimeZoneInfo.ClearCachedData()
    Console.WriteLine($"Current Time Zone: {TimeZoneInfo.Local.DisplayName}")
    Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("en-GB")
    Dim sr As New StreamReader(filenameTxt)
    Dim inputValues As String() = sr.ReadToEnd().Split({"|"c}, StringSplitOptions.RemoveEmptyEntries)
    sr.Close()
    Console.WriteLine($"The dates on an {Thread.CurrentThread.CurrentCulture.Name} system:")
    For Each inputValue In inputValues
        Dim dateValue As Date
        If DateTime.TryParse(inputValue, dateValue) Then
            Console.WriteLine($"'{inputValue}' --> {dateValue:f}")
        Else
            Console.WriteLine($"Cannot parse '{inputValue}'")
        End If
    Next
    Console.WriteLine("Restored dates...")
End Sub

Public Sub PersistAsInvariantStrings()
    SaveDatesAsInvariantStrings()
    RestoreDatesAsInvariantStrings()
End Sub

Private Sub SaveDatesAsInvariantStrings()
    Dim dates As Date() = {#6/14/2014 6:32AM#, #7/10/2014 11:49PM#,
                          #1/10/2015 1:16AM#, #12/20/2014 9:45PM#,
                          #6/2/2014 3:14PM#}
    Dim output As String = Nothing

    Console.WriteLine($"Current Time Zone: {TimeZoneInfo.Local.DisplayName}")
    Console.WriteLine($"The dates on an {Thread.CurrentThread.CurrentCulture.Name} system:")
    For ctr As Integer = 0 To dates.Length - 1
        Console.WriteLine(dates(ctr).ToString("f"))
        output += dates(ctr).ToUniversalTime().ToString("O", CultureInfo.InvariantCulture) +
                                   If(ctr <> dates.Length - 1, "|", "")
    Next
    Dim sw As New StreamWriter(filenameTxt)
    sw.Write(output)
    sw.Close()
    Console.WriteLine("Saved dates...")
End Sub

Private Sub RestoreDatesAsInvariantStrings()
    TimeZoneInfo.ClearCachedData()
    Console.WriteLine("Current Time Zone: {0}",
                    TimeZoneInfo.Local.DisplayName)
    Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("en-GB")
    Dim sr As New StreamReader(filenameTxt)
    Dim inputValues As String() = sr.ReadToEnd().Split({"|"c}, StringSplitOptions.RemoveEmptyEntries)
    sr.Close()
    Console.WriteLine($"The dates on an {Thread.CurrentThread.CurrentCulture.Name} system:")
    For Each inputValue In inputValues
        Dim dateValue As Date
        If DateTime.TryParseExact(inputValue, "O", CultureInfo.InvariantCulture,
                          DateTimeStyles.RoundtripKind, dateValue) Then
            Console.WriteLine($"'{inputValue}' --> {dateValue.ToLocalTime():f}")
        Else
            Console.WriteLine($"Cannot parse '{inputValue}'")
        End If
    Next
    Console.WriteLine("Restored dates...")
End Sub

Public Sub PersistAsIntegers()
    SaveDatesAsIntegers()
    RestoreDatesAsIntegers()
End Sub

Private Sub SaveDatesAsIntegers()
    Dim dates As Date() = {#6/14/2014 6:32AM#, #7/10/2014 11:49PM#,
                          #1/10/2015 1:16AM#, #12/20/2014 9:45PM#,
                          #6/2/2014 3:14PM#}

    Console.WriteLine($"Current Time Zone: {TimeZoneInfo.Local.DisplayName}")
    Console.WriteLine($"The dates on an {Thread.CurrentThread.CurrentCulture.Name} system:")
    Dim ticks(dates.Length - 1) As Long
    For ctr As Integer = 0 To dates.Length - 1
        Console.WriteLine(dates(ctr).ToString("f"))
        ticks(ctr) = dates(ctr).ToUniversalTime().Ticks
    Next
    Dim fs As New FileStream(filenameInts, FileMode.Create)
    Dim bw As New BinaryWriter(fs)
    bw.Write(ticks.Length)
    For Each tick In ticks
        bw.Write(tick)
    Next
    bw.Close()
    Console.WriteLine("Saved dates...")
End Sub

Private Sub RestoreDatesAsIntegers()
    TimeZoneInfo.ClearCachedData()
    Console.WriteLine($"Current Time Zone: {TimeZoneInfo.Local.DisplayName}")
    Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("en-GB")
    Dim fs As New FileStream(filenameInts, FileMode.Open)
    Dim br As New BinaryReader(fs)
    Dim items As Integer
    Dim dates As DateTime()

    Try
        items = br.ReadInt32()
        ReDim dates(items - 1)

        For ctr As Integer = 0 To items - 1
            Dim ticks As Long = br.ReadInt64()
            dates(ctr) = New DateTime(ticks).ToLocalTime()
        Next
    Catch e As EndOfStreamException
        Console.WriteLine("File corruption detected. Unable to restore data...")
        Exit Sub
    Catch e As IOException
        Console.WriteLine("Unspecified I/O error. Unable to restore data...")
        Exit Sub
    Catch e As OutOfMemoryException     'Thrown in array initialization.
        Console.WriteLine("File corruption detected. Unable to restore data...")
        Exit Sub
    Finally
        br.Close()
    End Try

    Console.WriteLine($"The dates on an {Thread.CurrentThread.CurrentCulture.Name} system:")
    For Each value In dates
        Console.WriteLine(value.ToString("f"))
    Next
    Console.WriteLine("Restored dates...")
End Sub

Public Sub PersistAsXml()
    ' Serialize the data.
    Dim leapYears As New List(Of DateTime)()
    For year As Integer = 2000 To 2100 Step 4
        If Date.IsLeapYear(year) Then
            leapYears.Add(New Date(year, 2, 29))
        End If
    Next
    Dim dateArray As DateTime() = leapYears.ToArray()

    Dim serializer As New XmlSerializer(dateArray.GetType())
    Dim sw As TextWriter = New StreamWriter(filenameXml)

    Try
        serializer.Serialize(sw, dateArray)
    Catch e As InvalidOperationException
        Console.WriteLine(e.InnerException.Message)
    Finally
        If sw IsNot Nothing Then sw.Close()
    End Try

    ' Deserialize the data.
    Dim deserializedDates As Date()
    Using fs As New FileStream(filenameXml, FileMode.Open)
        deserializedDates = CType(serializer.Deserialize(fs), Date())
    End Using

    ' Display the dates.
    Console.WriteLine($"Leap year days from 2000-2100 on an {Thread.CurrentThread.CurrentCulture.Name} system:")
    Dim nItems As Integer
    For Each dat In deserializedDates
        Console.Write($"   {dat:d}     ")
        nItems += 1
        If nItems Mod 5 = 0 Then Console.WriteLine()
    Next
End Sub

Public Sub PersistBinary()
    SaveDatesBinary()
    RestoreDatesBinary()
End Sub

Private Sub SaveDatesBinary()
    Dim dates As Date() = {#6/14/2014 6:32AM#, #7/10/2014 11:49PM#,
                          #1/10/2015 1:16AM#, #12/20/2014 9:45PM#,
                          #6/2/2014 3:14PM#}
    Dim fs As New FileStream(filenameBin, FileMode.Create)
    Dim bin As New BinaryFormatter()

    Console.WriteLine($"Current Time Zone: {TimeZoneInfo.Local.DisplayName}")
    Console.WriteLine("The dates on an {Thread.CurrentThread.CurrentCulture.Name} system:")
    For ctr As Integer = 0 To dates.Length - 1
        Console.WriteLine(dates(ctr).ToString("f"))
        dates(ctr) = dates(ctr).ToUniversalTime()
    Next
    bin.Serialize(fs, dates)
    fs.Close()
    Console.WriteLine("Saved dates...")
End Sub

Private Sub RestoreDatesBinary()
    TimeZoneInfo.ClearCachedData()
    Console.WriteLine("Current Time Zone: {TimeZoneInfo.Local.DisplayName}")
    Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("en-GB")

    Dim fs As New FileStream(filenameBin, FileMode.Open)
    Dim bin As New BinaryFormatter()
    Dim dates As DateTime() = DirectCast(bin.Deserialize(fs), Date())
    fs.Close()

    Console.WriteLine("The dates on an {Thread.CurrentThread.CurrentCulture.Name} system:")
    For Each value In dates
        Console.WriteLine(value.ToLocalTime().ToString("f"))
    Next
    Console.WriteLine("Restored dates...")
End Sub

Namespace DateTimeExtensions
    <Serializable> Public Structure DateWithTimeZone
        Private tz As TimeZoneInfo
        Private dt As DateTime

        Public Sub New(dateValue As DateTime, timeZone As TimeZoneInfo)
            dt = dateValue
            tz = If(timeZone, TimeZoneInfo.Local)
        End Sub

        Public Property TimeZone As TimeZoneInfo
            Get
                Return tz
            End Get
            Set
                tz = Value
            End Set
        End Property

        Public Property DateTime As Date
            Get
                Return dt
            End Get
            Set
                dt = Value
            End Set
        End Property
    End Structure
End Namespace

Public Sub SaveDateWithTimeZone()
    Dim dates As DateWithTimeZone() = {New DateWithTimeZone(#8/9/2014 7:30PM#,
                                      TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time")),
                                  New DateWithTimeZone(#8/15/2014 7:00PM#,
                                      TimeZoneInfo.FindSystemTimeZoneById("Pacific Standard Time")),
                                  New DateWithTimeZone(#8/22/2014 7:30PM#,
                                      TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time")),
                                  New DateWithTimeZone(#8/28/2014 7:00PM#,
                                      TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time"))}
    Dim fs As New FileStream(".\Schedule.bin", FileMode.Create)
    Dim formatter As New BinaryFormatter()
    Try
        formatter.Serialize(fs, dates)
    Catch e As SerializationException
        Console.WriteLine($"Serialization failed. Reason: {e.Message}")
    Finally
        If fs IsNot Nothing Then fs.Close()
    End Try
    ' Display dates.
    For Each dateInfo In dates
        Dim tz As TimeZoneInfo = dateInfo.TimeZone
        Console.WriteLine($"{dateInfo.DateTime} {If(tz.IsDaylightSavingTime(dateInfo.DateTime), tz.DaylightName, tz.StandardName)}")
    Next
End Sub

Public Sub RestoreDateWithTimeZone()
    Dim fs As FileStream
    If File.Exists(filename) Then
        fs = New FileStream(filename, FileMode.Open)
    Else
        Console.WriteLine("Unable to find file to deserialize.")
        Exit Sub
    End If

    Dim formatter As New BinaryFormatter()
    Dim dates As DateWithTimeZone ()= Nothing
    Try
        dates = DirectCast(formatter.Deserialize(fs), DateWithTimeZone())
        ' Display dates.
        For Each dateInfo In dates
            Dim tz As TimeZoneInfo = dateInfo.TimeZone
            Console.WriteLine($"{dateInfo.DateTime} {If(tz.IsDaylightSavingTime(dateInfo.DateTime), tz.DaylightName, tz.StandardName)}")
        Next
    Catch e As SerializationException
        Console.WriteLine("Deserialization failed. Reason: {e.Message}")
    Finally
        If fs IsNot Nothing Then fs.Close()
    End Try
End Sub

Public Shared Function RoughlyEquals(time As DateTime, timeWithWindow As DateTime,
                             windowInSeconds As Integer,
                             frequencyInSeconds As Integer) As Boolean
    Dim delta As Long = (timeWithWindow.Subtract(time)).TotalSeconds _
                                            Mod frequencyInSeconds

    If delta > windowInSeconds Then
        delta = frequencyInSeconds - delta
    End If

    Return Math.Abs(delta) < windowInSeconds
End Function

Public Shared Sub TestRoughlyEquals()
    Dim window As Integer = 10
    Dim freq As Integer = 60 * 60 * 2 ' 2 hours;
    Dim d1 As DateTime = DateTime.Now

    Dim d2 As DateTime = d1.AddSeconds(2 * window)
    Dim d3 As DateTime = d1.AddSeconds(-2 * window)
    Dim d4 As DateTime = d1.AddSeconds(window / 2)
    Dim d5 As DateTime = d1.AddSeconds(-window / 2)

    Dim d6 As DateTime = d1.AddHours(2).AddSeconds(2 * window)
    Dim d7 As DateTime = d1.AddHours(2).AddSeconds(-2 * window)
    Dim d8 As DateTime = d1.AddHours(2).AddSeconds(window / 2)
    Dim d9 As DateTime = d1.AddHours(2).AddSeconds(-window / 2)

    Console.WriteLine($"d1 ({d1}) ~= d1 ({d1}): {RoughlyEquals(d1, d1, window, freq)}")
    Console.WriteLine($"d1 ({d1}) ~= d2 ({d2}): {RoughlyEquals(d1, d2, window, freq)}")
    Console.WriteLine($"d1 ({d1}) ~= d3 ({d3}): {RoughlyEquals(d1, d3, window, freq)}")
    Console.WriteLine($"d1 ({d1}) ~= d4 ({d4}): {RoughlyEquals(d1, d4, window, freq)}")
    Console.WriteLine($"d1 ({d1}) ~= d5 ({d5}): {RoughlyEquals(d1, d5, window, freq)}")

    Console.WriteLine($"d1 ({d1}) ~= d6 ({d6}): {RoughlyEquals(d1, d6, window, freq)}")
    Console.WriteLine($"d1 ({d1}) ~= d7 ({d7}): {RoughlyEquals(d1, d7, window, freq)}")
    Console.WriteLine($"d1 ({d1}) ~= d8 ({d8}): {RoughlyEquals(d1, d8, window, freq)}")
    Console.WriteLine($"d1 ({d1}) ~= d9 ({d9}): {RoughlyEquals(d1, d9, window, freq)}")
End Sub

public class Test
   public Shared Sub Main
    Dim D As New DateTime(10000333333333333)
    Console.WriteLine("10000 ticks is " + D.Date())

   End Sub
End class