diff --git a/chrono/datetime.h b/chrono/datetime.h
index 6cee87f..a32c0f8 100644
--- a/chrono/datetime.h
+++ b/chrono/datetime.h
@@ -150,7 +150,7 @@ enum class DateTimeParts : std::uint64_t {
     Hour = (1 << 3), /**< the hour is present */
     Minute = (1 << 4), /**< the minute is present */
     Second = (1 << 5), /**< the second is present */
-    Millisecond = (1 << 6), /**< the millisecond is present */
+    SubSecond = (1 << 6), /**< the second contains a fractional part */
     DeltaHour = (1 << 7), /**< the timezone-delta hour is present */
     DeltaMinute = (1 << 8), /**< the timezone-delta minute is present */
 };
diff --git a/tests/chronotests.cpp b/tests/chronotests.cpp
index a826bd1..9294ce4 100644
--- a/tests/chronotests.cpp
+++ b/tests/chronotests.cpp
@@ -259,7 +259,7 @@ void ChronoTests::testDateTimeExpression()
     expr = DateTimeExpression::fromIsoString("1-1-1T0:0:0.0");
     CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
     CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
-    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Millisecond, expr.parts);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::SubSecond, expr.parts);
     expr = DateTimeExpression::fromIsoString("1-1-1T0:0:0.0+0");
     CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
     CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
@@ -300,7 +300,7 @@ void ChronoTests::testDateTimeExpression()
     expr = DateTimeExpression::fromString("1/1/1 0:0:0.0");
     CPPUNIT_ASSERT_EQUAL(DateTime(), expr.value);
     CPPUNIT_ASSERT_EQUAL(TimeSpan(), expr.delta);
-    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::Millisecond, expr.parts);
+    CPPUNIT_ASSERT_EQUAL(parts |= DateTimeParts::SubSecond, expr.parts);
 }
 
 /*!