LibCore: Add DateTime::from_timestamp(time_t)

Libraries/LibCore/DateTime.cpp

@@ -32,7 +32,11 @@ namespace Core {
 
 DateTime DateTime::now()
 {
-    auto timestamp = time(nullptr);
+    return from_timestamp(time(nullptr));
+}
+
+DateTime DateTime::from_timestamp(time_t timestamp)
+{
     struct tm tm;
     localtime_r(&timestamp, &tm);
     DateTime dt;

Libraries/LibCore/DateTime.h

@@ -46,6 +46,7 @@ public:
     String to_string() const;
 
     static DateTime now();
+    static DateTime from_timestamp(time_t);
 
 private:
     time_t m_timestamp { 0 };