General theme: fix syntax W3C markup and add improve 'Published' date

Signed-off-by: Jesús <heckyel@hyperbola.info>

youtube/util.py

@@ -1,3 +1,4 @@
+from datetime import datetime
 import settings
 import socks
 import sockshandler
@@ -607,3 +608,9 @@ def strip_non_ascii(string):
     ''' Returns the string without non ASCII characters'''
     stripped = (c for c in string if 0 < ord(c) < 127)
     return ''.join(stripped)
+
+
+def time_utc_isoformat(string):
+    t = datetime.strptime(string, '%Y-%m-%d')
+    t = t.astimezone().isoformat()
+    return t