Add support for encoding dates, courtesy of luddep.

Foundation/CPDate.j

@@ -185,4 +185,25 @@ var CPDateReferenceDate = new Date(Date.UTC(2001,1,1,0,0,0,0));
 
 @end
 
+var CPDateTimeKey = @"CPDateTimeKey";
+
+@implementation CPDate (CPCoding)
+
+- (id)initWithCoder:(CPCoder)aCoder
+{
+    if (self)
+    {
+        self.setTime([aCoder decodeIntForKey:CPDateTimeKey]);
+    }
+
+    return self;
+}
+
+- (void)encodeWithCoder:(CPCoder)aCoder
+{
+    [aCoder encodeInt:self.getTime() forKey:CPDateTimeKey];
+}
+
+@end
+
 Date.prototype.isa = CPDate;

Tests/Foundation/CPDateTest.j

@@ -43,6 +43,15 @@
     }
 }
 
+- (void)testEncoding
+{
+    var date = new Date(),
+        encodedDate = [CPKeyedArchiver archivedDataWithRootObject:date],
+        decodedDate = [CPKeyedUnarchiver unarchiveObjectWithData:encodedDate];
+
+    [self assert:date equals:decodedDate];
+}
+
 - (void)testDescription
 {
     // Unfortunately the result will be different depending on the testing machine's timezone.