diff --git a/boards/models/post.py b/boards/models/post.py
--- a/boards/models/post.py
+++ b/boards/models/post.py
@@ -43,9 +43,21 @@ REGEX_REPLY = re.compile('>>(\d+)')
 
 class PostManager(models.Manager):
 
+    def clear_ppd_cache_if_old(self):
+        """
+        If new post in the other day then current post, a day has changed
+        and we need to remove the PPD cache and recalculate PPD including the
+        previous day
+        """
+
+        today = datetime.now().date()
+        posts = self.filter(pub_time__gte=today)
+        if posts.exists():
+            cache.delete(CACHE_KEY_PPD)
+
     def create_post(self, title, text, image=None, thread=None,
                     ip=NO_IP, tags=None, user=None):
-        cache.delete(CACHE_KEY_PPD)
+        self.clear_ppd_cache_if_old()
 
         posting_time = timezone.now()
         if not thread:
@@ -62,7 +74,7 @@ class PostManager(models.Manager):
                            thread_new=thread,
                            image=image,
                            poster_ip=ip,
-                           poster_user_agent=UNKNOWN_UA,
+                           poster_user_agent=UNKNOWN_UA, # TODO Get UA at last!
                            last_edit_time=posting_time,
                            user=user)
 
@@ -162,7 +174,7 @@ class PostManager(models.Manager):
         return int(math.ceil(thread_count / float(settings.THREADS_PER_PAGE)))
 
     def get_posts_per_day(self):
-        """Get count of posts for the current day"""
+        """Get average count of posts per day for the last 7 days"""
 
         ppd = cache.get(CACHE_KEY_PPD)
         if ppd: