Fix wrong time offset on DST. (Closes: #4615)

warden_client/warden_client.py

@@ -645,10 +645,10 @@ class Client(object):
 
 
 def format_timestamp(epoch=None, utc=True, utcoffset=None):
-    if utcoffset is None:
-        utcoffset = -(time.altzone if time.daylight else time.timezone)
     if epoch is None:
         epoch = time.time()
+    if utcoffset is None:
+        utcoffset = -(time.altzone if time.daylight and time.localtime(epoch).tm_isdst else time.timezone)
     if utc:
         epoch += utcoffset
     us = int(epoch % 1 * 1000000 + 0.5)