support for 12 hour time Locale setting (hourCycle)

Sources/iCalendarParser/Models/DateTimeType.swift

@@ -1,5 +1,24 @@
 import Foundation
 
+
+extension Locale {
+    static func is12HoursFormat() -> Bool {
+        DateFormatter.dateFormat(fromTemplate: "j", options: 0, locale: Locale.current)?.range(of: "a") != nil
+    }
+
+    static func is24HoursFormat() -> Bool {
+        !Self.is12HoursFormat()
+    }
+
+    func is12HoursFormat() -> Bool {
+        DateFormatter.dateFormat(fromTemplate: "j", options: 0, locale: self)?.range(of: "a") != nil
+    }
+
+    func is24HoursFormat() -> Bool {
+        !is12HoursFormat()
+    }
+}
+
 public enum DateTimeType {
     case date
     case dateTime
@@ -17,7 +36,8 @@ public enum DateTimeType {
         } else {
             formatter.timeZone = TimeZone(abbreviation: "UTC")
         }
-
+
+
         formatter.dateFormat = {
             switch self {
             case .date:
@@ -28,7 +48,15 @@ public enum DateTimeType {
                     : "yyyyMMdd'T'HHmmss"
             }
         }()
-
+
+        formatter.locale = {
+            if Locale.is12HoursFormat() {
+                return Locale(identifier: "en_US_POSIX")
+            } else {
+                return Locale.current
+            }
+        }()
+
         return formatter
     }
 }

Tests/iCalendarParserTests/DateTimeTypeTests.swift

@@ -26,4 +26,18 @@ final class DateTimeTypeTests: XCTestCase {
         let wrongDate = dateTime.type.dateFormatter().date(from: "19700327T020000")
         XCTAssertNotEqual(dateTime.date, wrongDate)
     }
+
+    func testCorrectHourCycle() {
+        // to test this toggle off/on 24-hour time in settings
+        let property = ICProperty("DTSTART", "19700329T020000")
+        let dateTime = PropertyBuilder.buildDateTime(from: property)!
+        let dateFormatter = dateTime.type.dateFormatter()
+        let currentLocale = Locale.current
+        if (currentLocale.is12HoursFormat()){
+            XCTAssert(dateFormatter.locale.hourCycle == .oneToTwelve)
+        }
+        else {
+            XCTAssert(dateFormatter.locale.hourCycle == .zeroToTwentyThree)
+        }
+    }
 }