diff --git a/demo/moulinrouge/tests.py b/demo/moulinrouge/tests.py
index 2c944cc..1a0a997 100644
--- a/demo/moulinrouge/tests.py
+++ b/demo/moulinrouge/tests.py
@@ -463,6 +463,7 @@ def get_test_routes(app):
         chart.add(10 * '1b', [(4, 12), (5, 8), (6, 4)], secondary=True)
         chart.add(10 * '2b', [(3, 24), (0, 17), (12, 9)], secondary=True)
         chart.add(10 * '2', [(8, 23), (21, 1), (5, 0)])
+        chart.value_formatter = lambda x: str(int(x)) + '+'
         return chart.render_response()
 
     @app.route('/test/box')
@@ -930,7 +931,7 @@ def get_test_routes(app):
             (datetime(2013, 1, 12, 8), 412),
             (datetime(2013, 1, 12, 8, tzinfo=tzn4), 823)
         ])
-        line.x_value_formatter = lambda x: x.isoformat()  # strftime("%Y-%m-%d")
+        # line.x_value_formatter = lambda x: x.isoformat()  # strftime("%Y-%m-%d")
         line.x_label_rotation = 45
         return line.render_response()
 
diff --git a/pygal/_compat.py b/pygal/_compat.py
index 7d53ab0..997335d 100644
--- a/pygal/_compat.py
+++ b/pygal/_compat.py
@@ -16,11 +16,12 @@
 #
 # You should have received a copy of the GNU Lesser General Public License
 # along with pygal. If not, see <http://www.gnu.org/licenses/>.
+from __future__ import division
 """Various hacks for transparent python 2 / python 3 support"""
 
 import sys
 from collections import Iterable
-import time
+from datetime import datetime, timedelta, tzinfo
 
 
 if sys.version_info[0] == 3:
@@ -70,16 +71,32 @@ def total_seconds(td):
         ) / 10 ** 6
     return td.total_seconds()
 
+try:
+    from datetime import timezone
+    utc = timezone.utc
+except ImportError:
+    class UTC(tzinfo):
+        def tzname(self, dt):
+            return 'UTC'
+
+        def utcoffset(self, dt):
+            return timedelta(0)
+
+        def dst(self, dt):
+            return None
+    utc = UTC()
+
 
 def timestamp(x):
     """Get a timestamp from a date in python 3 and python 2"""
+    if x.tzinfo is None:
+        # Naive dates to utc
+        x = x.replace(tzinfo=utc)
+
     if hasattr(x, 'timestamp'):
-        from datetime import timezone
-        if x.tzinfo is None:
-            return x.replace(tzinfo=timezone.utc).timestamp()
         return x.timestamp()
     else:
-        return time.mktime(x.utctimetuple())
+        return total_seconds(x - datetime(1970, 1, 1, tzinfo=utc))
 
 try:
     from urllib import quote_plus
diff --git a/pygal/test/test_date.py b/pygal/test/test_date.py
index d1a4858..5950700 100644
--- a/pygal/test/test_date.py
+++ b/pygal/test/test_date.py
@@ -20,6 +20,7 @@
 """Date related charts tests"""
 
 from pygal import DateLine, TimeLine, DateTimeLine, TimeDeltaLine
+from pygal._compat import timestamp, utc
 from pygal.test.utils import texts
 from datetime import datetime, date, time, timedelta
 
@@ -158,3 +159,17 @@ def test_date_labels():
                 '2013-01-01',
                 '2013-02-01',
                 '2013-03-01']
+
+
+def test_utc_timestamping():
+    assert timestamp(
+        datetime(2017, 7, 14, 2, 40).replace(tzinfo=utc)
+    ) == 1500000000
+
+    for d in (
+        datetime.now(),
+        datetime.utcnow(),
+        datetime(1999, 12, 31, 23, 59, 59),
+        datetime(2000, 1, 1, 0, 0, 0)
+    ):
+        assert datetime.utcfromtimestamp(timestamp(d)) == d
diff --git a/tox.ini b/tox.ini
index 4e7dfb5..969c033 100644
--- a/tox.ini
+++ b/tox.ini
@@ -14,5 +14,5 @@ setenv =
     COVERAGE_FILE=.cov-{envname}
 
 commands =
-  coverage run --source=pygal {envbindir}/py.test pygal/test --junitxml=junit-{envname}.xml --flake8
+  coverage run --source=pygal {envbindir}/py.test {posargs:pygal/test} --junitxml=junit-{envname}.xml --flake8
   coverage xml -o coverage-{envname}.xml