diff --git a/Sources/Schedule/Interval.swift b/Sources/Schedule/Interval.swift
index 6dc1baa..67339e3 100644
--- a/Sources/Schedule/Interval.swift
+++ b/Sources/Schedule/Interval.swift
@@ -102,6 +102,16 @@ extension Interval {
         self.init(nanoseconds: seconds * pow(10, 9))
     }
 
+    /// The length of this interval in microseconds.
+    public var microseconds: Double {
+        return nanoseconds / pow(10, 3)
+    }
+
+    /// The length of this interval in milliseconds.
+    public var milliseconds: Double {
+        return nanoseconds / pow(10, 6)
+    }
+
     /// The length of this interval in seconds.
     public var seconds: Double {
         return nanoseconds / pow(10, 9)
diff --git a/Sources/Schedule/Period.swift b/Sources/Schedule/Period.swift
index 3ad6ad5..c189adc 100644
--- a/Sources/Schedule/Period.swift
+++ b/Sources/Schedule/Period.swift
@@ -137,9 +137,9 @@ public struct Period {
     public func tidied(to unit: Unit) -> Period {
         var period = self
         if case .nanosecond = unit { return period }
-        if period.nanoseconds.magnitude >= UInt(NSEC_PER_SEC) {
-            period.seconds += period.nanoseconds / Int(NSEC_PER_SEC)
-            period.nanoseconds %= Int(NSEC_PER_SEC)
+        if period.nanoseconds.magnitude >= UInt(1.second.nanoseconds) {
+            period.seconds += period.nanoseconds / Int(1.second.nanoseconds)
+            period.nanoseconds %= Int(1.second.nanoseconds)
         }
 
         if case .second = unit { return period }
diff --git a/Sources/Schedule/Time.swift b/Sources/Schedule/Time.swift
index d1e74ac..c8d8069 100644
--- a/Sources/Schedule/Time.swift
+++ b/Sources/Schedule/Time.swift
@@ -30,10 +30,10 @@ public struct Time {
     ///     Time(hour: 25)              => nil
     ///     Time(hour: 1, minute: 61)   => nil
     public init?(hour: Int, minute: Int = 0, second: Int = 0, nanosecond: Int = 0) {
-        guard (0..<24).contains(hour) else { return nil }
-        guard (0..<60).contains(minute) else { return nil }
-        guard (0..<60).contains(second) else { return nil }
-        guard (0..<Int(NSEC_PER_SEC)).contains(nanosecond) else { return nil }
+        guard (0..<24).contains(hour),
+              (0..<60).contains(minute),
+              (0..<60).contains(second),
+              (0..<Int(1.second.nanoseconds)).contains(nanosecond) else { return nil }
 
         self.hour = hour
         self.minute = minute
@@ -88,7 +88,7 @@ public struct Time {
                 fmt = fmt.replacingOccurrences(of: "HH", with: "hh")
                 fmt += " a"
             }
-            var formatter: DateFormatter! = Time.FormatterCache.object(forKey: fmt as NSString)
+            var formatter: DateFormatter! = Time.FormatterCache.object(forKey: NSString(string: fmt))
             if formatter == nil {
                 formatter = DateFormatter()
                 formatter?.locale = Locale(identifier: "en_US_POSIX")
@@ -97,7 +97,7 @@ public struct Time {
                 formatter.dateFormat = fmt
             }
             if let date = formatter.date(from: string) {
-                Time.FormatterCache.setObject(formatter, forKey: fmt as NSString)
+                Time.FormatterCache.setObject(formatter, forKey: NSString(string: fmt))
                 let components = Calendar.gregorian.dateComponents(in: TimeZone.autoupdatingCurrent, from: date)
                 if let hour = components.hour,
                    let minute = components.minute,
diff --git a/Tests/ScheduleTests/DateTimeTests.swift b/Tests/ScheduleTests/DateTimeTests.swift
index b2bb703..f64138e 100644
--- a/Tests/ScheduleTests/DateTimeTests.swift
+++ b/Tests/ScheduleTests/DateTimeTests.swift
@@ -13,7 +13,7 @@ final class DateTimeTests: XCTestCase {
     func testInterval() {
 
         XCTAssertTrue((-1).second.isNegative)
-        XCTAssertEqual(1.1.second.magnitude, 1.1 * Constants.NSEC_PER_SEC)
+        XCTAssertEqual(1.1.second.magnitude, 1.1.second.nanoseconds)
 
         XCTAssertTrue(1.1.second.isLonger(than: 1.0.second))
         XCTAssertTrue(3.days.isShorter(than: 1.week))
@@ -26,13 +26,13 @@ final class DateTimeTests: XCTestCase {
         XCTAssertEqual(-(1.second), (-1).second)
 
         XCTAssertEqual(1.nanoseconds, Interval(nanoseconds: 1))
-        XCTAssertEqual(2.microseconds, Interval(nanoseconds: 2 * Constants.NSEC_PER_USEC))
-        XCTAssertEqual(3.milliseconds, Interval(nanoseconds: 3 * Constants.NSEC_PER_MSEC))
-        XCTAssertEqual(4.seconds, Interval(nanoseconds: 4 * Constants.NSEC_PER_SEC))
-        XCTAssertEqual(5.1.minutes, Interval(nanoseconds: 5.1 * Constants.NSEC_PER_M))
-        XCTAssertEqual(6.2.hours, Interval(nanoseconds: 6.2 * Constants.NSEC_PER_H))
-        XCTAssertEqual(7.3.days, Interval(nanoseconds: 7.3 * Constants.NSEC_PER_D))
-        XCTAssertEqual(8.4.weeks, Interval(nanoseconds: 8.4 * Constants.NSEC_PER_W))
+        XCTAssertEqual(2.microseconds, Interval(nanoseconds: 2.microseconds.nanoseconds))
+        XCTAssertEqual(3.milliseconds, Interval(nanoseconds: 3.milliseconds.nanoseconds))
+        XCTAssertEqual(4.seconds, Interval(nanoseconds: 4.seconds.nanoseconds))
+        XCTAssertEqual(5.1.minutes, Interval(nanoseconds: 5.1.minutes.nanoseconds))
+        XCTAssertEqual(6.2.hours, Interval(nanoseconds: 6.2.hours.nanoseconds))
+        XCTAssertEqual(7.3.days, Interval(nanoseconds: 7.3.days.nanoseconds))
+        XCTAssertEqual(8.4.weeks, Interval(nanoseconds: 8.4.weeks.nanoseconds))
     }
 
     func testTime() {
@@ -45,7 +45,7 @@ final class DateTimeTests: XCTestCase {
         XCTAssertEqual(t1?.minute, 12)
         XCTAssertEqual(t1?.second, 13)
         if let i = t1?.nanosecond.nanoseconds {
-            XCTAssertTrue(i.isAlmostEqual(to: (0.456 * Constants.NSEC_PER_SEC).nanoseconds, leeway: 0.001.seconds))
+            XCTAssertTrue(i.isAlmostEqual(to: (0.456.second.nanoseconds).nanoseconds, leeway: 0.001.seconds))
         }
 
         let t2 = Time("11 pm")
diff --git a/Tests/ScheduleTests/Misc.swift b/Tests/ScheduleTests/Misc.swift
index 4140632..2ee8672 100644
--- a/Tests/ScheduleTests/Misc.swift
+++ b/Tests/ScheduleTests/Misc.swift
@@ -65,14 +65,3 @@ extension Schedule {
         return makeIterator().isAlmostEqual(to: schedule.makeIterator(), leeway: leeway)
     }
 }
-
-struct Constants {
-
-    static let NSEC_PER_USEC = Double(Foundation.NSEC_PER_USEC)
-    static let NSEC_PER_MSEC = Double(Foundation.NSEC_PER_MSEC)
-    static let NSEC_PER_SEC = Double(Foundation.NSEC_PER_SEC)
-    static let NSEC_PER_M = Double(Foundation.NSEC_PER_SEC) * 60
-    static let NSEC_PER_H = Double(Foundation.NSEC_PER_SEC) * 60 * 60
-    static let NSEC_PER_D = Double(Foundation.NSEC_PER_SEC) * 60 * 60 * 24
-    static let NSEC_PER_W = Double(Foundation.NSEC_PER_SEC) * 60 * 60 * 24 * 7
-}