Make calendar to use UTC timezone instead of the user's current one.

Author: soberman

Example/Koyomi.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>

Koyomi/DateModel.swift

@@ -307,7 +307,11 @@ final class DateModel: NSObject {
 // MARK: - Private Methods -
 
 private extension DateModel {
-    var calendar: Calendar { return Calendar.current }
+    var calendar: Calendar {
+		var utcCalendar = Calendar.current
+		utcCalendar.timeZone = TimeZone(abbreviation: "UTC")!
+		return utcCalendar
+	}
 
     func setup() {
         selectedDates = [:]