diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..5c2d62e
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1 @@
+iso8601==0.1.10
\ No newline at end of file
diff --git a/toggl/base.py b/toggl/base.py
index 4e49ef1..431b24d 100644
--- a/toggl/base.py
+++ b/toggl/base.py
@@ -60,7 +60,12 @@ def __init__(self, api, **kwargs):
         self._update_attrs(kwargs)
 
     def _update_attrs(self, attrs):
-        for k, v in attrs.iteritems():
+        try:
+            iteritems = dict.items # Python 3
+        except AttributeError:
+            iteritems = dict.iteritems # Python 2
+
+        for k, v in iteritems(attrs):
             try:
                 v = iso8601.parse_date(v)
                 attrs[k] = v
diff --git a/toggl/reports.py b/toggl/reports.py
index ae62ea0..ed26f2b 100644
--- a/toggl/reports.py
+++ b/toggl/reports.py
@@ -2,6 +2,8 @@
 
 from .session import Session
 
+import sys
+
 __all__ = ['Reports']
 
 
@@ -16,31 +18,36 @@ def parse_val(v):
             else:
                 return v
 
-        for k, v in attribs.iteritems():
+        try:
+            iteritems = dict.items # Python 3
+        except AttributeError:
+            iteritems = dict.iteritems # Python 2
+
+        for k, v in iteritems(attribs):
             if isinstance(v, list):
                 attribs[k] = [parse_val(el) for el in v]
             elif isinstance(v, dict):
                 attribs[k] = parse_val(v)
         self.__dict__.update(attribs)
 
-    @property
-    def keys(self):
-        return self.__dict__.keys()
-
-    def __unicode__(self):
-        if hasattr(self, '_unicode_value'):
-            if self._unicode_value is None:
-                return '(none)'
+    if sys.version_info[0] < 3:
+        @property
+        def keys(self):
+            return self.__dict__.keys()
+
+    if sys.version_info[0] < 3:
+        def __unicode__(self):
+            if hasattr(self, '_unicode_value'):
+                if self._unicode_value is None:
+                    return '(none)'
+                else:
+                    return self._unicode_value
             else:
-                return self._unicode_value
-        else:
-            return super(Node, self).__unicode__()
+                return super(Node, self).__unicode__()
 
-    def __str__(self):
-        return unicode(self).encode('utf-8')
-
-    def __contains__(self, key):
-        return key in self.__dict__
+    if sys.version_info[0] < 3:
+        def __str__(self):
+            return self.__unicode__().encode('utf-8')
 
 
 class Reports(object):
@@ -68,15 +75,23 @@ def request(self, type, workspace_id=None, **params):
                 raise ValueError('missing workspace ID')
             workspace_id = self.workspace_id
 
-        for k, v in params.iteritems():
+        try:
+            iteritems = dict.items # Python 3
+        except AttributeError:
+            iteritems = dict.iteritems # Python 2
+
+        for k, v in iteritems(params):
             if isinstance(v, datetime) or isinstance(v, date):
                 params[k] = v.strftime('%Y-%m-%d')
 
         params['workspace_id'] = workspace_id
         params['user_agent'] = self.USER_AGENT
 
-        data = self.session.get(type, **params)
-        return Node(**data)
+        if sys.version_info[0] < 3:
+            data = self.session.get(type, **params)
+            return Node(**data)
+        else:
+            return self.session.get(type, **params)
 
     @classmethod
     def _get_totals(cls, data):
diff --git a/toggl/session.py b/toggl/session.py
index 12d8702..120f862 100644
--- a/toggl/session.py
+++ b/toggl/session.py
@@ -1,5 +1,8 @@
 import requests
-from urllib import urlencode
+try:
+    from urllib import urlencode
+except ImportError:
+    from urllib.parse import urlencode
 import logging
 import json