diff --git a/src/calibre/utils/date.py b/src/calibre/utils/date.py
index aa7714df2d..50b98b39b8 100644
--- a/src/calibre/utils/date.py
+++ b/src/calibre/utils/date.py
@@ -118,8 +118,13 @@ def utcnow():
 def utcfromtimestamp(stamp):
     return datetime.utcfromtimestamp(stamp).replace(tzinfo=_utc_tz)
 
-def format_date(dt, format):
+def format_date(dt, format, assume_utc=False, as_utc=False):
     ''' Return a date formatted as a string using a subset of Qt's formatting codes '''
+    if hasattr(dt, 'tzinfo'):
+        if dt.tzinfo is None:
+            dt = dt.replace(tzinfo=_utc_tz if assume_utc else
+                    _local_tz)
+        dt = dt.astimezone(_utc_tz if as_utc else _local_tz)
     strf = partial(strftime, t=dt.timetuple())
 
     def format_day(mo):