System.TimeZoneInfo F# snippets

snippets/fsharp/System/TimeZoneInfo+AdjustmentRule/Overview/System.TimeZone2.AdjustmentRule.Class.fs

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+module program
+
+open System
+open System.Globalization
+
+let createCustomTimeZone () =
+    // <Snippet1>
+    // Create alternate Central Standard Time to include historical time zone information
+    let delta = TimeSpan(1, 0, 0)
+    let adjustmentList = ResizeArray()
+
+    // Define end rule (for 1976-2006)
+    let transitionRuleEnd = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(DateTime(1, 1, 1, 2, 0, 0), 10, 5, DayOfWeek.Sunday)
+    // Define rule (1976-1986)
+    let transitionRuleStart = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(DateTime(1, 1, 1, 2, 0, 0), 04, 05, DayOfWeek.Sunday)
+    TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(DateTime(1976, 1, 1), DateTime(1986, 12, 31), delta, transitionRuleStart, transitionRuleEnd)
+    |> adjustmentList.Add
+    // Define rule (1987-2006)  
+    let transitionRuleStart = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(DateTime(1, 1, 1, 2, 0, 0), 04, 01, DayOfWeek.Sunday)
+    TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(DateTime(1987, 1, 1), DateTime(2006, 12, 31), delta, transitionRuleStart, transitionRuleEnd)
+    |> adjustmentList.Add
+    // Define rule (2007- )  
+    let transitionRuleStart = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(DateTime(1, 1, 1, 2, 0, 0), 03, 02, DayOfWeek.Sunday)
+    let transitionRuleEnd = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(DateTime(1, 1, 1, 2, 0, 0), 11, 01, DayOfWeek.Sunday)
+    TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(DateTime(2007, 01, 01), DateTime.MaxValue.Date, delta, transitionRuleStart, transitionRuleEnd)
+    |> adjustmentList.Add
+
+    // Create custom U.S. Central Standard Time zone         
+    TimeZoneInfo.CreateCustomTimeZone("Central Standard Time", TimeSpan(-6, 0, 0), 
+                                      "(GMT-06:00) Central Time (US Only)", "Central Standard Time", 
+                                      "Central Daylight Time", adjustmentList.ToArray())       
+    // </Snippet1>   
+
+let compareRulesForEquality () =
+    // <Snippet2>
+    // Get CST, Canadian CST, and Mexican CST adjustment rules
+    let usCstAdjustments =
+        let timeZoneName = "Central Standard Time"
+        try
+            TimeZoneInfo.FindSystemTimeZoneById(timeZoneName).GetAdjustmentRules()
+        with
+        | :? TimeZoneNotFoundException ->
+            printfn $"The {timeZoneName} time zone is not defined in the registry."
+            null
+        | :? InvalidTimeZoneException ->
+            printfn $"Data for the {timeZoneName} time zone is invalid."
+            null
+    let canCstAdjustments = 
+        let timeZoneName = "Canada Central Standard Time"
+        try
+            TimeZoneInfo.FindSystemTimeZoneById(timeZoneName).GetAdjustmentRules()
+        with
+        | :? TimeZoneNotFoundException ->
+            printfn $"The {timeZoneName} time zone is not defined in the registry."
+            null
+        | :? InvalidTimeZoneException ->
+            printfn $"Data for the {timeZoneName} time zone is invalid."
+            null
+    let mexCstAdjustments = 
+        let timeZoneName = "Central Standard Time (Mexico)"
+        try
+            TimeZoneInfo.FindSystemTimeZoneById(timeZoneName).GetAdjustmentRules()
+        with
+        | :? TimeZoneNotFoundException ->
+            printfn $"The {timeZoneName} time zone is not defined in the registry."
+            null
+        | :? InvalidTimeZoneException ->
+            printfn $"Data for the {timeZoneName} time zone is invalid."
+            null
+    // Determine if CST and other time zones have the same rules
+    for rule in usCstAdjustments do
+        printfn $"Comparing Central Standard Time rule for {rule.DateStart:d} to {rule.DateEnd:d} with:"
+        // Compare with Canada Central Standard Time
+        if canCstAdjustments.Length = 0 then
+            printfn "   Canada Central Standard Time has no adjustment rules."
+        else
+            for canRule in canCstAdjustments do
+                printfn $"""   Canadian CST for {canRule.DateStart:d} to {canRule.DateEnd:d}: {if rule.Equals canRule then "Equal" else "Not Equal"}"""
+
+        // Compare with Mexico Central Standard Time
+        if mexCstAdjustments.Length = 0 then
+            printfn "   Mexican Central Standard Time has no adjustment rules."
+        else
+            for mexRule in mexCstAdjustments do
+                printfn $"""   Mexican CST for {mexRule.DateStart:d} to {mexRule.DateEnd:d}: {if rule.Equals mexRule then "Equal" else "Not Equal"}"""
+    // This code displays the following output to the console:
+    // 
+    // Comparing Central Standard Time rule for 1/1/0001 to 12/31/9999 with:
+    //    Canada Central Standard Time has no adjustment rules.
+    //    Mexican CST for 1/1/0001 to 12/31/9999: Equal
+    // </Snippet2>
+
+// <Snippet3>   
+type WeekOfMonth = 
+    | First = 1
+    | Second = 2
+    | Third = 3
+    | Fourth = 4
+    | Last = 5
+
+let showStartAndEndDates () =
+    // Get all time zones from system
+    let timeZones = TimeZoneInfo.GetSystemTimeZones()
+    let monthNames = CultureInfo.CurrentCulture.DateTimeFormat.MonthNames
+    // Get each time zone
+    for timeZone in timeZones do
+        let adjustments = timeZone.GetAdjustmentRules()
+        // Display message for time zones with no adjustments
+        if adjustments.Length = 0 then
+            printfn $"{timeZone.StandardName} has no adjustment rules"
+        else
+            // Handle time zones with 1 or 2+ adjustments differently
+            let mutable ctr = 0
+            let showCount, spacer = 
+                if adjustments.Length > 1 then
+                    true, "   "
+                else 
+                    false, ""
+            printfn $"{timeZone.StandardName} Adjustment rules"
+
+            // Iterate adjustment rules
+            for adjustment in adjustments do
+                if showCount then
+                    printfn $"   Adjustment rule #{ctr + 1}"
+                    ctr <- ctr + 1
+                // Display general adjustment information
+                printfn $"{spacer}   Start Date: {adjustment.DateStart:D}"
+                printfn $"{spacer}   End Date: {adjustment.DateEnd:D}"
+                printfn $"{spacer}   Time Change: {adjustment.DaylightDelta.Hours}:{adjustment.DaylightDelta.Minutes:D2} hours"
+                // Get transition start information
+                let transitionStart = adjustment.DaylightTransitionStart
+                printf $"{spacer}   Annual Start: "
+                if transitionStart.IsFixedDateRule then
+                    printfn $"On {monthNames[transitionStart.Month - 1]} {transitionStart.Day} at {transitionStart.TimeOfDay:t}"
+                else
+                    printfn $"The {transitionStart.Week |> enum<WeekOfMonth>} {transitionStart.DayOfWeek} of {monthNames[transitionStart.Month - 1]} at {transitionStart.TimeOfDay:t}"
+                // Get transition end information
+                let transitionEnd = adjustment.DaylightTransitionEnd
+                printf $"{spacer}   Annual End: "
+                if transitionEnd.IsFixedDateRule then
+                    printfn $"On {monthNames[transitionEnd.Month - 1]} {transitionEnd.Day} at {transitionEnd.TimeOfDay:t}"
+                else
+                    printfn $"The {enum<WeekOfMonth> transitionEnd.Week} {transitionEnd.DayOfWeek} of {monthNames[transitionEnd.Month - 1]} at {transitionEnd.TimeOfDay:t}" 
+        Console.WriteLine()
+// </Snippet3>
+createCustomTimeZone () |> ignore
+compareRulesForEquality ()
+showStartAndEndDates ()

snippets/fsharp/System/TimeZoneInfo+AdjustmentRule/Overview/fs.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="System.TimeZone2.AdjustmentRule.Class.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/TimeZoneInfo/BaseUtcOffset/ShowTimeZoneNames1.fs

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+module ShowTimeZoneNames1
+
+// <Snippet2>
+open System
+
+let localZone = TimeZoneInfo.Local
+printfn $"Local Time Zone ID: {localZone.Id}"
+printfn $"   Display Name is: {localZone.DisplayName}."
+printfn $"   Standard name is: {localZone.StandardName}."
+printfn $"   Daylight saving name is: {localZone.DaylightName}."
+// The example displays output like the following:
+//     Local Time Zone ID: Pacific Standard Time
+//        Display Name is: (UTC-08:00) Pacific Time (US & Canada).
+//        Standard name is: Pacific Standard Time.
+//        Daylight saving name is: Pacific Daylight Time.
+// </Snippet2>

snippets/fsharp/System/TimeZoneInfo/BaseUtcOffset/TimeZone2_Examples.fs

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+module TimeZone2
+
+open System
+
+do
+    // <Snippet1>
+    let localZone = TimeZoneInfo.Local
+    printfn $"""The {localZone.DisplayName} time zone is {abs localZone.BaseUtcOffset.Hours}:{abs localZone.BaseUtcOffset.Minutes} {if localZone.BaseUtcOffset >= TimeSpan.Zero then "later" else "earlier"} than Coordinated Universal Time."""
+    // </Snippet1>                  
+
+do
+    let localZone = TimeZoneInfo.Local
+    printfn $"Local Time Zone ID: {localZone.Id}"
+    printfn $"   Display Name is: {localZone.DisplayName}."
+    printfn $"   Standard name is: {localZone.StandardName}."
+    printfn $"   Daylight saving name is: {localZone.DaylightName}."
+
+do
+    // <Snippet3>
+    let universalZone = TimeZoneInfo.Utc
+    printfn $"The universal time zone is {universalZone.DisplayName}."
+    printfn $"Its standard name is {universalZone.StandardName}."
+    printfn $"Its daylight savings name is {universalZone.DaylightName}."
+    // </Snippet3>
+
+do
+    // <Snippet4>
+    let zones = TimeZoneInfo.GetSystemTimeZones()
+    for zone in zones do
+        if not zone.SupportsDaylightSavingTime then
+            Console.WriteLine zone.DisplayName
+    // </Snippet4> 
+
+do
+    // <Snippet5>
+    let zones = TimeZoneInfo.GetSystemTimeZones()
+    printfn $"The local system has the following {zones.Count} time zones"
+    for zone in zones do
+        printfn $"{zone.Id}"
+    // </Snippet5>
+
+do
+    // <Snippet7> 
+    let thisTimeZone = TimeZoneInfo.Local
+    let zone1 = TimeZoneInfo.FindSystemTimeZoneById "Pacific Standard Time"
+    let zone2 = TimeZoneInfo.FindSystemTimeZoneById "Eastern Standard Time"
+    printfn $"{thisTimeZone.Equals zone1}"
+    printfn $"{thisTimeZone.Equals zone2}"
+    // </Snippet7>
+
+do
+    // <Snippet8>
+    // Specify DateTimeKind in Date constructor
+    let baseTime = DateTime(2007, 11, 4, 0, 59, 00, DateTimeKind.Unspecified)
+
+    // Get Pacific Standard Time zone
+    let pstZone = TimeZoneInfo.FindSystemTimeZoneById "Pacific Standard Time"
+
+    // List possible ambiguous times for 63-minute interval, from 12:59 AM to 2:01 AM 
+    for i = 0 to 62 do
+    // Because of assignment, newTime.Kind is also DateTimeKind.Unspecified
+        let newTime = baseTime.AddMinutes i   
+        printfn $"{newTime} is ambiguous: {pstZone.IsAmbiguousTime newTime}"
+    // </Snippet8>      
+
+do
+    // <Snippet9>
+    // Specify DateTimeKind in Date constructor
+    let baseTime = DateTime(2007, 3, 11, 1, 59, 0, DateTimeKind.Unspecified)
+
+    // Get Pacific Standard Time zone
+    let pstZone = TimeZoneInfo.FindSystemTimeZoneById "Pacific Standard Time"
+
+    // List possible invalid times for a 63-minute interval, from 1:59 AM to 3:01 AM
+    for i = 0 to 62 do
+        // Because of assignment, newTime.Kind is also DateTimeKind.Unspecified
+        let newTime = baseTime.AddMinutes i
+        printfn $"{newTime} is invalid: {pstZone.IsInvalidTime newTime}"
+    // </Snippet9>

snippets/fsharp/System/TimeZoneInfo/BaseUtcOffset/fs.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="TimeZone2_Examples.fs" />
+    <Compile Include="ShowTimeZoneNames1.fs" />
+    <Compile Include="getsystemtimezones1.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/TimeZoneInfo/BaseUtcOffset/getsystemtimezones1.fs

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+module getsystemtimezones1
+
+// <Snippet6>
+open System
+open System.Globalization
+open System.IO
+open System.Collections.ObjectModel
+
+[<EntryPoint>]
+let main _ =
+    let OUTPUTFILENAME = @"C:\Temp\TimeZoneInfo.txt"
+
+    let dateFormats = CultureInfo.CurrentCulture.DateTimeFormat
+    let timeZones = TimeZoneInfo.GetSystemTimeZones() 
+    use sw = new StreamWriter(OUTPUTFILENAME, false)
+
+    for timeZone in timeZones do
+        let hasDST = timeZone.SupportsDaylightSavingTime
+        let offsetFromUtc = timeZone.BaseUtcOffset
+
+        sw.WriteLine $"ID: {timeZone.Id}"
+        sw.WriteLine $"   Display Name: {timeZone.DisplayName, 40}"
+        sw.WriteLine $"   Standard Name: {timeZone.StandardName, 39}"
+        sw.Write $"   Daylight Name: {timeZone.DaylightName, 39}"
+        sw.Write(if hasDST then "   ***Has " else "   ***Does Not Have ")
+        sw.WriteLine "Daylight Saving Time***"
+        let offsetString = $"{offsetFromUtc.Hours} hours, {offsetFromUtc.Minutes} minutes"
+        sw.WriteLine $"   Offset from UTC: {offsetString, 40}"
+        let adjustRules = timeZone.GetAdjustmentRules()
+        sw.WriteLine $"   Number of adjustment rules: {adjustRules.Length, 26}"
+        if adjustRules.Length > 0 then
+            sw.WriteLine "   Adjustment Rules:"
+            for rule in adjustRules do
+                let transTimeStart = rule.DaylightTransitionStart
+                let transTimeEnd = rule.DaylightTransitionEnd 
+
+                sw.WriteLine $"      From {rule.DateStart} to {rule.DateEnd}"
+                sw.WriteLine $"      Delta: {rule.DaylightDelta}"
+                if not transTimeStart.IsFixedDateRule then
+                    sw.WriteLine $"      Begins at {transTimeStart.TimeOfDay:t} on {transTimeStart.DayOfWeek} of week {transTimeStart.Week} of {dateFormats.MonthNames[transTimeStart.Month - 1]}"
+                    sw.WriteLine $"      Ends at {transTimeEnd.TimeOfDay:t} on {transTimeEnd.DayOfWeek} of week {transTimeEnd.Week} of {dateFormats.MonthNames[transTimeEnd.Month - 1]}"
+                else
+                    sw.WriteLine $"      Begins at {transTimeStart.TimeOfDay:t} on {transTimeStart.Day} {dateFormats.MonthNames[transTimeStart.Month - 1]}"
+                    sw.WriteLine $"      Ends at {transTimeEnd.TimeOfDay:t} on {transTimeEnd.Day} {dateFormats.MonthNames[transTimeEnd.Month - 1]}"
+    0
+// </Snippet6>

snippets/fsharp/System/TimeZoneInfo/ClearCachedData/System.TimeZone2.BestPractices.fs

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+module program
+
+// <Snippet1>
+open System
+
+let cst = TimeZoneInfo.FindSystemTimeZoneById "Central Standard Time"
+let local = TimeZoneInfo.Local
+printfn $"{TimeZoneInfo.ConvertTime(DateTime.Now, local, cst)}"
+
+TimeZoneInfo.ClearCachedData()
+try
+   printfn $"{TimeZoneInfo.ConvertTime(DateTime.Now, local, cst)}"
+with :? ArgumentException as e ->
+   printfn $"{e.GetType().Name}\n   {e.Message}"
+// </Snippet1>

snippets/fsharp/System/TimeZoneInfo/ClearCachedData/fs.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="System.TimeZone2.BestPractices.fs" />
+  </ItemGroup>
+</Project>

snippets/fsharp/System/TimeZoneInfo/ConvertTime/TimeZone2Concepts.fs

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+module TimeZone2Concepts
+
+open System
+
+do
+    // <Snippet8>
+    let timeUtc = DateTime.UtcNow
+    try
+        let cstZone = TimeZoneInfo.FindSystemTimeZoneById "Central Standard Time"
+        let cstTime = TimeZoneInfo.ConvertTimeFromUtc(timeUtc, cstZone)
+        printfn $"The date and time are {cstTime} {if cstZone.IsDaylightSavingTime cstTime then cstZone.DaylightName else cstZone.StandardName}."
+    with
+    | :? TimeZoneNotFoundException ->
+        printfn "The registry does not define the Central Standard Time zone."
+    | :? InvalidTimeZoneException ->
+        printfn "Registry data on the Central Standard Time zone has been corrupted."
+    // </Snippet8>
+
+do
+    // <Snippet9>
+    let hwTime = DateTime(2007, 02, 01, 08, 00, 00)
+    try
+        let hwZone = TimeZoneInfo.FindSystemTimeZoneById "Hawaiian Standard Time"
+        printfn $"{hwTime} {if hwZone.IsDaylightSavingTime hwTime then hwZone.DaylightName else hwZone.StandardName} is {TimeZoneInfo.ConvertTime(hwTime, hwZone, TimeZoneInfo.Local)} local time." 
+    with
+    | :? TimeZoneNotFoundException ->
+        printfn "The registry does not define the Hawaiian Standard Time zone."
+    | :? InvalidTimeZoneException ->
+        printfn "Registry data on the Hawaiian Standard Time zone has been corrupted."
+    // </Snippet9>