Update readme

Author: mattjohnsonpint

README.md

@@ -13,17 +13,20 @@
 PM> Install-Package TimeZoneConverter
 ```
 
-This library should be compatible with .NET Standard 1.1 and greater, as well as .NET Framework 3.5 and greater.
-See the [.NET Standard Platform Support Matrix][1] for further details about .NET Standard,
-and please raise an issue if you encounter any compatibility errors.
+As of version 4.0.0, *TimeZoneConverter* works with all of the following:
 
-#### Important note on .NET 6+
+- .NET 5 or greater
+- .NET Core 2.0 or greater
+- .NET Framework 4.6.1 and greater
+
+Note that .NET Framework versions less than 4.6.1 are no longer supported.
 
-.NET 6 will have built-in support for IANA and Windows time zones in a cross-platform manner, removing the need for the TimeZoneConverter library.
-**If you are planning to use .NET 6 (or higher), you don't need to use the TimeZoneConverter library!**
+#### Important note on .NET 6+
 
-Both automatic time zone conversion and APIs for manual time zone conversion are included with .NET as of .NET 6 Preview 4.
-You can read more about it in [the blog post here](https://devblogs.microsoft.com/dotnet/date-time-and-time-zone-enhancements-in-net-6/#time-zone-conversion-apis).
+.NET 6 has built-in support for IANA and Windows time zones in a cross-platform manner, removing the need for the TimeZoneConverter library.
+It relies on [.NET's ICU integration](https://docs.microsoft.com/dotnet/core/extensions/globalization-icu) to perform this functionality.
+See [the .NET blog](https://devblogs.microsoft.com/dotnet/date-time-and-time-zone-enhancements-in-net-6/#time-zone-conversion-apis) for details.
+**If you are targeting only .NET 6 (or higher), and you have either platform-provided or App-local ICU enabled, you don't need to use the TimeZoneConverter library!**
 
 #### Note on OS Data Dependencies
 
@@ -40,11 +43,17 @@ For example, the Alpine Linux Docker images for .NET Core no longer ship with `t
 PM> Install-Package TimeZoneConverter.Posix
 ```
 
-This library should be compatible with .NET Standard 1.3 and greater, as well as .NET Framework 4.5 and greater.
-See the [.NET Standard Platform Support Matrix][1] for further details about .NET Standard,
-and please raise an issue if you encounter any compatibility errors.
+This is a separate helper library that is maintained in the same repository.  You only need it if you require support for POSIX time zones.
+
+As of version 3.0.0, *TimeZoneConverter.Posix* works with all of the following:
+
+- .NET 5 or greater
+- .NET Core 2.0 or greater
+- .NET Framework 4.6.1 and greater
+
+Note that .NET Framework versions less than 4.6.1 are no longer supported.
 
-Note that `TimeZoneConverter.Posix` takes a dependency on both `TimeZoneConverter` and [Noda Time][2].
+Also note that `TimeZoneConverter.Posix` takes a dependency on both `TimeZoneConverter` and [Noda Time][2].
 
 ## Notes
 
@@ -90,8 +99,6 @@ string tz = TZConvert.WindowsToIana("Eastern Standard Time", "CA");
 ```
 
 Get a `TimeZoneInfo` object from .NET Core, regardless of what OS you are running on:  
-*Helps with .NET Runtime issue [#18644][8]*  
-***This function is only available for .NET Standard 1.3+ or full .NET Framework targets***
 
 ```csharp
 // Either of these will work on any platform:
@@ -155,15 +162,14 @@ string posix = PosixTimeZone.FromTimeZoneInfo(TimeZoneInfo.Local);
 
 ## License
 
-This library is provided free of charge, under the terms of the [MIT license][9].
+This library is provided free of charge, under the terms of the [MIT license][8].
 
 
 [1]: https://docs.microsoft.com/en-us/dotnet/articles/standard/library
 [2]: https://nodatime.org
-[3]: http://cldr.unicode.org
+[3]: https://cldr.unicode.org
 [4]: https://iana.org/time-zones
 [5]: https://aka.ms/dstblog
 [6]: https://github.com/rails/rails/blob/master/activesupport/lib/active_support/values/time_zone.rb
 [7]: https://support.microsoft.com/en-us/help/4051956/time-zone-and-dst-changes-in-windows-for-northern-cyprus-sudan-and-ton
-[8]: https://github.com/dotnet/runtime/issues/18644
-[9]: https://github.com/mattjohnsonpint/TimeZoneConverter/blob/main/LICENSE.txt
+[8]: https://github.com/mattjohnsonpint/TimeZoneConverter/blob/main/LICENSE.txt