DateFormatter's timezone changes (#11)

* Apply timezone fixes from Eugene

* updates pod version

Colander.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = 'Colander'
-  s.version          = '0.2.3'
+  s.version          = '0.2.4'
   s.summary          = 'A highly customizable iOS calendar view'
 
   s.description      = <<-DESC

Colander/Classes/DateExtensions.swift

@@ -1,18 +1,26 @@
 import SwiftDate
 
-extension Calendar {
+internal extension Calendar {
     static let gregorian = Calendar(identifier: Calendar.Identifier.gregorian)
 }
 
-extension Date {
+internal extension Date {
     var beginningOfMonth: Date {
-        var firstDayOfStartMonth = Calendar.gregorian.dateComponents( [.era, .year, .month], from: self)
+        var calendar = Calendar(identifier: Calendar.Identifier.gregorian)
+        if let timeZone = TimeZone(secondsFromGMT: 0) {
+            calendar.timeZone = timeZone
+        }
+        var firstDayOfStartMonth = calendar.dateComponents( [.era, .year, .month], from: self)
         firstDayOfStartMonth.day = 1
-        return Calendar.gregorian.date(from: firstDayOfStartMonth) ?? Date.nowAt(.startOfMonth)
+        return calendar.date(from: firstDayOfStartMonth) ?? Date.nowAt(.startOfMonth)
     }
 
     var beginningOfWeek: Date {
-        return Calendar.gregorian.date(from: Calendar.gregorian.dateComponents([.yearForWeekOfYear, .weekOfYear], from: self)) ?? Date.nowAt(.startOfWeek)
+        var calendar = Calendar(identifier: Calendar.Identifier.gregorian)
+        if let timeZone = TimeZone(secondsFromGMT: 0) {
+            calendar.timeZone = timeZone
+        }
+        return calendar.date(from: calendar.dateComponents([.yearForWeekOfYear, .weekOfYear], from: self)) ?? Date.nowAt(.startOfWeek)
     }
 
     var endOfWeek: Date {

Colander/Classes/MonthInfo.swift

@@ -15,15 +15,18 @@ struct MonthInfo {
     let firstDayWeekdayIndex: Int
     let numberOfDaysInMonth: Int
 
-    init(forMonthContaining date: Date, with calendar: Calendar = Calendar.gregorian) throws {
-        guard let numberOfDaysInMonth = calendar.range(of: .day, in: .month, for: date)?.count else {
+    init(forMonthContaining date: Date, with calendar: Calendar? = nil) throws {
+        var targetCalendar = calendar ?? Calendar(identifier: Calendar.Identifier.gregorian)
+        targetCalendar.timeZone = calendar?.timeZone ?? TimeZone(secondsFromGMT: 0)!
+
+        guard let numberOfDaysInMonth = targetCalendar.range(of: .day, in: .month, for: date)?.count else {
             throw DateError.Generic("Could not determine number of days in month for \(date)")
         }
 
         let beginningOfMonth = date.beginningOfMonth
         self.startDate = beginningOfMonth
         self.endDate = beginningOfMonth + numberOfDaysInMonth.days
-        self.firstDayWeekdayIndex = calendar.component(.weekday, from: startDate) - 1 // 1-indexed to 0-indexed
+        self.firstDayWeekdayIndex = targetCalendar.component(.weekday, from: startDate) - 1 // 1-indexed to 0-indexed
         self.numberOfDaysInMonth = numberOfDaysInMonth
     }
 }

Example/Tests/Date+Mock.swift

@@ -10,8 +10,13 @@ extension Date {
     ///   - day: the desired day
     /// - Returns: a new instance of `Date` with the given components
     static func mockDateFrom(year: Int, month: Int, day: Int, hour: Int = 0) -> Date {
-        let c = DateComponents(year: year, month: month, day: day, hour: hour)
-        let dateInRegion : DateInRegion = DateInRegion(components: c, region: nil)!
+        var components = DateComponents(year: year, month: month, day: day, hour: hour)
+        // nsdate is timezone independent, essentially representing GMT,
+        // so make sure the calendar is parsing the date in GMT as well
+        if let timeZone = TimeZone(secondsFromGMT: 0) {
+            components.timeZone = timeZone
+        }
+        let dateInRegion : DateInRegion = DateInRegion(components: components, region: nil)!
         return dateInRegion.date
     }
 }

Example/Tests/MonthInfoSpec.swift

@@ -57,6 +57,14 @@ class MonthInfoSpec: QuickSpec {
                 // Feburary 2017 has 28 days
                 expect(monthInfo.numberOfDaysInMonth).to(equal(29))
             }
+
+            it("Correctly decides beginningOfMonth for startDate") {
+                // September 10, 2019
+                let monthInfo = try! MonthInfo(forMonthContaining: Date.mockDateFrom(year: 2019, month: 9, day: 10))
+
+                // September 1, 2019 is a Sunday
+                expect(monthInfo.startDate.beginningOfMonth.day).to(equal(1))
+            }
         }
     }
 }