Set en_US_POSIX locale for date formatters (#289)

* Set en_US_POSIX locale for date formatters

* Add changelog entry for #289

Author: mattt

Changelog.md

@@ -26,6 +26,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed layout of HTML output on large displays.
   #251 by @Lukas-Stuehrk and @mattt.
 
+### Changed
+
+- Changed date formatters to use `en_US_POSIX` locale instead of current locale.
+  #289 by @mattt.
+
 ## [1.0.0-beta.6] - 2021-04-24
 
 ### Added

Sources/swift-doc/Supporting Types/Pages/FooterPage.swift

@@ -4,13 +4,15 @@ import HypertextLiteral
 
 fileprivate let dateFormatter: DateFormatter = {
     var dateFormatter = DateFormatter()
+    dateFormatter.locale = Locale(identifier: "en_US_POSIX")
     dateFormatter.dateStyle = .long
     dateFormatter.timeStyle = .none
     return dateFormatter
 }()
 
 fileprivate let timestampDateFormatter: DateFormatter = {
     var dateFormatter = DateFormatter()
+    dateFormatter.locale = Locale(identifier: "en_US_POSIX")
     dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
     return dateFormatter
 }()