diff --git a/fail2ban/server/strptime.py b/fail2ban/server/strptime.py
index 56f1c753..2da27c58 100644
--- a/fail2ban/server/strptime.py
+++ b/fail2ban/server/strptime.py
@@ -107,17 +107,17 @@ def zone2offset(tz, dt):
 		been validated already)
 	dt: datetime instance for offset computation
 	"""
-	if isinstance(tz, basestring):
-		if len(tz) <= 3: # short tz (hh only)
-			# [+-]hh --> [+-]hh*60
-			return int(tz)*60
-		if tz[3] != ':':
-			# [+-]hhmm --> [+-]1 * (hh*60 + mm)
-			return int(tz[0]+'1') * (int(tz[1:3])*60 + int(tz[3:5]))
-		else:
-			# [+-]hh:mm --> [+-]1 * (hh*60 + mm)
-			return int(tz[0]+'1') * (int(tz[1:3])*60 + int(tz[4:6]))
-	return tz
+	if isinstance(tz, int):
+		return tz
+	if len(tz) <= 3: # short tz (hh only)
+		# [+-]hh --> [+-]hh*60
+		return int(tz)*60
+	if tz[3] != ':':
+		# [+-]hhmm --> [+-]1 * (hh*60 + mm)
+		return (-1 if tz[0] == '-' else 1) * (int(tz[1:3])*60 + int(tz[3:5]))
+	else:
+		# [+-]hh:mm --> [+-]1 * (hh*60 + mm)
+		return (-1 if tz[0] == '-' else 1) * (int(tz[1:3])*60 + int(tz[4:6]))
 
 def reGroupDictStrptime(found_dict, msec=False, default_tz=None):
 	"""Return time from dictionary of strptime fields
diff --git a/fail2ban/tests/datedetectortestcase.py b/fail2ban/tests/datedetectortestcase.py
index cbf1ac21..56970ac5 100644
--- a/fail2ban/tests/datedetectortestcase.py
+++ b/fail2ban/tests/datedetectortestcase.py
@@ -99,16 +99,16 @@ class DateDetectorTest(LogCaptureTestCase):
 			('UTC',      logdt, dtUTC), # UTC
 			('UTC-0430', logdt, dt(2017, 1, 23, 19, 30)),
 			('GMT+12',   logdt, dt(2017, 1, 23, 3, 0)),
-			(None,			 logdt, dt(2017, 1, 23, 14, 0)), # default CET in our test-framework
+			(None,       logdt, dt(2017, 1, 23, 14, 0)), # default CET in our test-framework
 			('UTC+0300', logdt+' GMT', dtUTC), # GMT wins
 			('UTC',      logdt+' GMT', dtUTC), # GMT wins
 			('UTC-0430', logdt+' GMT', dtUTC), # GMT wins
-			(None,			 logdt+' GMT', dtUTC), # GMT wins
+			(None,       logdt+' GMT', dtUTC), # GMT wins
 			('UTC',      logdt+' -1045', dt(2017, 1, 24, 1, 45)), # -1045 wins
-			(None,			 logdt+' -10:45', dt(2017, 1, 24, 1, 45)), # -1045 wins
+			(None,       logdt+' -10:45', dt(2017, 1, 24, 1, 45)), # -1045 wins
 			('UTC',      logdt+' +0945', dt(2017, 1, 23, 5, 15)), # +0945 wins
-			(None,			 logdt+' +09:45', dt(2017, 1, 23, 5, 15)), # +0945 wins
-			(None,			 logdt+' Z', dtUTC), # Z wins (UTC)
+			(None,       logdt+' +09:45', dt(2017, 1, 23, 5, 15)), # +0945 wins
+			(None,       logdt+' Z', dtUTC), # Z wins (UTC)
 		):
 			logSys.debug('== test %r with TZ %r', log, tz)
 			dd.default_tz=tz; datelog, _ = dd.getTime(log)