diff --git a/lib/mongo/util/bson.rb b/lib/mongo/util/bson.rb
index 023136c..241e02e 100644
--- a/lib/mongo/util/bson.rb
+++ b/lib/mongo/util/bson.rb
@@ -248,8 +248,10 @@ class BSON
   end
 
   def deserialize_date_data(buf)
-    millisecs = buf.get_long()
-    Time.at(millisecs.to_f / 1000.0).utc # at() takes fractional seconds
+    unsigned = buf.get_long()
+    # see note for deserialize_number_long_data below
+    milliseconds = unsigned >= 2 ** 64 / 2 ? unsigned - 2**64 : unsigned
+    Time.at(milliseconds.to_f / 1000.0).utc # at() takes fractional seconds
   end
 
   def deserialize_boolean_data(buf)
diff --git a/test/test_bson.rb b/test/test_bson.rb
index 30af1b1..a947f3c 100644
--- a/test/test_bson.rb
+++ b/test/test_bson.rb
@@ -124,6 +124,14 @@ class BSONTest < Test::Unit::TestCase
     assert doc2['date'].utc?
   end
 
+  def test_date_before_epoch
+    doc = {'date' => Time.utc(1600)}
+    @b.serialize(doc)
+    doc2 = @b.deserialize
+    # Mongo only stores up to the millisecond
+    assert_in_delta doc['date'], doc2['date'], 0.001
+  end
+
   def test_dbref
     oid = ObjectID.new
     doc = {}
diff --git a/test/test_collection.rb b/test/test_collection.rb
index 79e5e18..0180652 100644
--- a/test/test_collection.rb
+++ b/test/test_collection.rb
@@ -182,6 +182,11 @@ class TestCollection < Test::Unit::TestCase
     assert c.closed?
   end
 
+  def test_saving_dates_pre_epoch
+    @@test.save({'date' => Time.utc(1600)})
+    assert_in_delta Time.utc(1600), @@test.find_one()["date"], 0.001
+  end
+
   def test_save_symbol_find_string
     @@test.save(:foo => :mike)