add all api to sort by month

Sources/App/Libraries/SwiftDate/Date/Date+Math.swift

@@ -0,0 +1,40 @@
+//
+//  SwiftDate
+//  Parse, validate, manipulate, and display dates, time and timezones in Swift
+//
+//  Created by Daniele Margutti
+//   - Web: https://www.danielemargutti.com
+//   - Twitter: https://twitter.com/danielemargutti
+//   - Mail: hello@danielemargutti.com
+//
+//  Copyright © 2019 Daniele Margutti. Licensed under MIT License.
+//
+
+import Foundation
+
+/// Subtracts two dates and returns the relative components from `lhs` to `rhs`.
+/// Follows this mathematical pattern:
+///     let difference = lhs - rhs
+///     rhs + difference = lhs
+public func - (lhs: Date, rhs: Date) -> DateComponents {
+	return SwiftDate.defaultRegion.calendar.dateComponents(DateComponents.allComponentsSet, from: rhs, to: lhs)
+}
+
+/// Adds date components to a date and returns a new date.
+public func + (lhs: Date, rhs: DateComponents) -> Date {
+	return rhs.from(lhs)!
+}
+
+/// Adds date components to a date and returns a new date.
+public func + (lhs: DateComponents, rhs: Date) -> Date {
+	return (rhs + lhs)
+}
+
+/// Subtracts date components from a date and returns a new date.
+public func - (lhs: Date, rhs: DateComponents) -> Date {
+	return (lhs + (-rhs))
+}
+
+public func + (lhs: Date, rhs: TimeInterval) -> Date {
+	return lhs.addingTimeInterval(rhs)
+}