How to Calculate the Difference Between Time Zones in VB6

Hours separate countries that have different time zones.

Visual Basic comes with a number of tools for analyzing time zones. The "TimeZoneInfo" variable type lets you define specific time zones as variables. Operations let you check the time in these various time zones and convert these times to their own variables. A separate set of operations manipulate times and dates, finding the difference between the two times you defined from the different time zones.

Instructions

1. Create a Visual Basic program from the following Microsoft code to list your registry's time zone IDs:

   Imports System.Collections.ObjectModel

   Imports System.Globalization

   Imports System.IO

   Module Example

   Public Sub Main()

   Const OUTPUTFILENAME As String = "C:\Temp\TimeZoneInfo.txt"

   Dim timeZones As ReadOnlyCollection(Of TimeZoneInfo) = TimeZoneInfo.GetSystemTimeZones()

   Dim sw As StreamWriter = New StreamWriter(OUTPUTFILENAME, False)

   For Each timeZone As TimeZoneInfo in timeZones

   Dim hasDST As Boolean = timeZone.SupportsDaylightSavingTime

   Dim offsetFromUtc As TimeSpan = timeZone.BaseUtcOffset

   Dim adjustRules() As System.TimeZoneInfo.AdjustmentRule

   Dim offsetString As String

   sw.WriteLine("ID: {0}", timeZone.Id)

   sw.WriteLine(" Display Name: {0, 40}", timeZone.DisplayName)

   sw.WriteLine(" Standard Name: {0, 39}", timeZone.StandardName)

   sw.Write(" Daylight Name: {0, 39}", timeZone.DaylightName)

   sw.Write(iif(hasDST, " ***Has ", " ***Does Not Have "))

   sw.WriteLine("Daylight Saving Time***")

   offsetString = String.Format("{0} hours, {1} minutes", offsetFromUtc.Hours, offsetFromUtc.Minutes)

   sw.WriteLine(" Offset from UTC: {0, 40}", offsetString)

   adjustRules = timeZone.GetAdjustmentRules()

   sw.WriteLine(" Number of adjustment rules: {0, 26}", adjustRules.Length)

   If adjustRules.Length > 0 Then

   sw.WriteLine(" Adjustment Rules:")

   For Each rule As TimeZoneInfo.AdjustmentRule In adjustRules

   Dim transTimeStart As TimeZoneInfo.TransitionTime = rule.DaylightTransitionStart

   Dim transTimeEnd As TimeZoneInfo.TransitionTime = rule.DaylightTransitionEnd

   sw.WriteLine(" From {0} to {1}", rule.DateStart, rule.DateEnd)

   sw.WriteLine(" Delta: {0}", rule.DaylightDelta)

   If Not transTimeStart.IsFixedDateRule

   sw.WriteLine(" Begins at {0:t} on {1} of week {2} of {3}", transTimeStart.TimeOfDay, _

   transTimeStart.DayOfWeek, _

   transTimeStart.Week, _

   MonthName(transTimeStart.Month))

   sw.WriteLine(" Ends at {0:t} on {1} of week {2} of {3}", transTimeEnd.TimeOfDay, _

   transTimeEnd.DayOfWeek, _

   transTimeEnd.Week, _

   MonthName(transTimeEnd.Month))

   Else

   sw.WriteLine(" Begins at {0:t} on {1} {2}", transTimeStart.TimeOfDay, _

   transTimeStart.Day, _

   MonthName(transTimeStart.Month))

   sw.WriteLine(" Ends at {0:t} on {1} {2}", transTimeEnd.TimeOfDay, _

   transTimeEnd.Day, _

   MonthName(transTimeEnd.Month))

   End If

   Next

   End If

   Next

   sw.Close()

2. Create the following Visual Basic program:

   Public Shared Sub() Main

   Dim timeZone1 As TimeZoneInfo

   timeZone1 = TimeZoneInfo.FindSystemTimeZoneByID("Pacific Standard Time")

   Dim timeZone2 As TimeZoneInfo

   timeZone2 = TimeZoneInfo.FindSydtemTimeZoneByID("Mountain Standard Time")

   Dim difference As Long = DateDiff(DateInterval.Hour, 1stTimeZone.StandardTime, 2ndTimeZone.StandardTime)

   Console.WriteLine(difference)

3. Replace "Pacific Standard Time" with the first time zone you want to compare, taking care to exactly reproduce the ID from the list from Step 1.

4. Replace "Mountain Standard Time" with the second time zone you want to compare.

5. Run the program.

References

• "Visual Basic 2008 Recipes: A Problem-Solution Approach"; Todd Herman and Allen Jones; 2008
• "Mastering Microsoft Visual Basic 2008"; Evangelos Petroutsos; 2008
• Microsoft Support: DateDiff Function (Visual Basic)

Resources

• Microsoft Support: TimeZoneInfo.GetSystemTimeZones Method