diff --git a/Sources/Basics/Cancellator.swift b/Sources/Basics/Cancellator.swift
index 805d7976655..9cb30617d57 100644
--- a/Sources/Basics/Cancellator.swift
+++ b/Sources/Basics/Cancellator.swift
@@ -128,7 +128,7 @@ public final class Cancellator: Cancellable, Sendable {
         self.register(name: "\(process.arguments.joined(separator: " "))", handler: process.terminate)
     }
 
-    #if !os(iOS) && !os(watchOS) && !os(tvOS)
+    #if !canImport(Darwin) || os(macOS)
     public func register(_ process: Foundation.Process) -> RegistrationKey? {
         self.register(name: "\(process.description)", handler: process.terminate(timeout:))
     }
@@ -245,7 +245,7 @@ extension AsyncProcess {
     }
 }
 
-#if !os(iOS) && !os(watchOS) && !os(tvOS)
+#if !canImport(Darwin) || os(macOS)
 extension Foundation.Process {
     fileprivate func terminate(timeout: DispatchTime) {
         guard self.isRunning else {
diff --git a/Sources/Basics/DispatchTimeInterval+Extensions.swift b/Sources/Basics/DispatchTimeInterval+Extensions.swift
index 07f5be1f575..4c74b3bc61e 100644
--- a/Sources/Basics/DispatchTimeInterval+Extensions.swift
+++ b/Sources/Basics/DispatchTimeInterval+Extensions.swift
@@ -86,7 +86,7 @@ extension DispatchTimeInterval {
             return String(format: "%.2f", Double(value) / Double(1_000_000_000)) + "s"
         case .never:
             return "n/a"
-        #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
+        #if canImport(Darwin)
         @unknown default:
             return "n/a"
         #endif
diff --git a/Sources/Basics/JSON+Extensions.swift b/Sources/Basics/JSON+Extensions.swift
index 3aa38d77a71..94c35fe7442 100644
--- a/Sources/Basics/JSON+Extensions.swift
+++ b/Sources/Basics/JSON+Extensions.swift
@@ -15,64 +15,8 @@ import class Foundation.DateFormatter
 import class Foundation.JSONDecoder
 import class Foundation.JSONEncoder
 
-#if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
-extension DateFormatter {
-    public static let iso8601: DateFormatter = {
-        let dateFormatter = DateFormatter()
-        dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
-        return dateFormatter
-    }()
-}
-
-extension JSONEncoder.DateEncodingStrategy {
-    public static let customISO8601 = custom {
-        var container = $1.singleValueContainer()
-        try container.encode(DateFormatter.iso8601.string(from: $0))
-    }
-}
-
-extension JSONDecoder.DateDecodingStrategy {
-    public static let customISO8601 = custom {
-        let container = try $0.singleValueContainer()
-        let string = try container.decode(String.self)
-        if let date = DateFormatter.iso8601.date(from: string) {
-            return date
-        }
-        throw DecodingError.dataCorruptedError(in: container, debugDescription: "Invalid date: \(string)")
-    }
-}
-#endif
-
-extension JSONEncoder.DateEncodingStrategy {
-    public static var safeISO8601: JSONEncoder.DateEncodingStrategy {
-        #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
-        if #available(macOS 10.12, iOS 10.0, watchOS 3.0, tvOS 10.0, *) {
-            return .iso8601
-        } else {
-            return .customISO8601
-        }
-        #else
-        return .iso8601
-        #endif
-    }
-}
-
-extension JSONDecoder.DateDecodingStrategy {
-    public static var safeISO8601: JSONDecoder.DateDecodingStrategy {
-        #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
-        if #available(macOS 10.12, iOS 10.0, watchOS 3.0, tvOS 10.0, *) {
-            return .iso8601
-        } else {
-            return .customISO8601
-        }
-        #else
-        return .iso8601
-        #endif
-    }
-}
-
 extension JSONDecoder {
-    public static func makeWithDefaults(dateDecodingStrategy: DateDecodingStrategy = .safeISO8601) -> JSONDecoder {
+    public static func makeWithDefaults(dateDecodingStrategy: DateDecodingStrategy = .iso8601) -> JSONDecoder {
         let decoder = JSONDecoder()
         decoder.dateDecodingStrategy = dateDecodingStrategy
         return decoder
@@ -82,7 +26,7 @@ extension JSONDecoder {
 extension JSONEncoder {
     public static func makeWithDefaults(
         prettified: Bool = true,
-        dateEncodingStrategy: DateEncodingStrategy = .safeISO8601
+        dateEncodingStrategy: DateEncodingStrategy = .iso8601
     ) -> JSONEncoder {
         Self.makeWithDefaults(
             sortKeys: prettified,
@@ -96,19 +40,13 @@ extension JSONEncoder {
         sortKeys: Bool,
         prettyPrint: Bool,
         escapeSlashes: Bool,
-        dateEncodingStrategy: DateEncodingStrategy = .safeISO8601
+        dateEncodingStrategy: DateEncodingStrategy = .iso8601
     ) -> JSONEncoder {
         let encoder = JSONEncoder()
         var outputFormatting: JSONEncoder.OutputFormatting = []
 
         if sortKeys {
-            #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
-            if #available(macOS 10.15, iOS 11.0, watchOS 4.0, tvOS 11.0, *) {
-                outputFormatting.insert(.sortedKeys)
-            }
-            #else
             outputFormatting.insert(.sortedKeys)
-            #endif
         }
         if prettyPrint {
             outputFormatting.insert(.prettyPrinted)
diff --git a/Sources/SPMBuildCore/Plugins/DefaultPluginScriptRunner.swift b/Sources/SPMBuildCore/Plugins/DefaultPluginScriptRunner.swift
index 223c60a229c..38da378e0ac 100644
--- a/Sources/SPMBuildCore/Plugins/DefaultPluginScriptRunner.swift
+++ b/Sources/SPMBuildCore/Plugins/DefaultPluginScriptRunner.swift
@@ -433,7 +433,7 @@ public struct DefaultPluginScriptRunner: PluginScriptRunner, Cancellable {
         delegate: PluginScriptRunnerDelegate,
         completion: @escaping (Result<Int32, Error>) -> Void
     ) {
-#if os(iOS) || os(watchOS) || os(tvOS)
+#if canImport(Darwin) && !os(macOS)
         callbackQueue.async {
             completion(.failure(DefaultPluginScriptRunnerError.pluginUnavailable(reason: "subprocess invocations are unavailable on this platform")))
         }
diff --git a/Sources/_InternalTestSupport/MockBuildTestHelper.swift b/Sources/_InternalTestSupport/MockBuildTestHelper.swift
index 47dc0cb4e1a..5a29ebadf33 100644
--- a/Sources/_InternalTestSupport/MockBuildTestHelper.swift
+++ b/Sources/_InternalTestSupport/MockBuildTestHelper.swift
@@ -23,7 +23,7 @@ import XCTest
 public struct MockToolchain: PackageModel.Toolchain {
     #if os(Windows)
     public let librarianPath = AbsolutePath("/fake/path/to/link.exe")
-    #elseif os(iOS) || os(macOS) || os(tvOS) || os(watchOS)
+    #elseif canImport(Darwin)
     public let librarianPath = AbsolutePath("/fake/path/to/libtool")
     #else
     public let librarianPath = AbsolutePath("/fake/path/to/llvm-ar")