diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,11 @@
+50200.0.1
+=========
+
+Bug fixes:
+ * Fix the specification of the QuerySince time for fetching channel
+   posts.  The previous version generated a user-displayable date-time
+   which contained spaces and created a malformed URL as well as not
+   being in the proper format for the server.
 
 50200.0.0
 =========
diff --git a/mattermost-api.cabal b/mattermost-api.cabal
--- a/mattermost-api.cabal
+++ b/mattermost-api.cabal
@@ -1,5 +1,5 @@
 name:                mattermost-api
-version:             50200.0.0
+version:             50200.0.1
 synopsis:            Client API for Mattermost chat system
 description:         Client API for Mattermost chat system
 license:             BSD3
diff --git a/src/Network/Mattermost/Endpoints.hs b/src/Network/Mattermost/Endpoints.hs
--- a/src/Network/Mattermost/Endpoints.hs
+++ b/src/Network/Mattermost/Endpoints.hs
@@ -9,7 +9,6 @@
 import           Data.Sequence (Seq)
 import           Data.Text (Text)
 import qualified Data.Text as T
-import           Data.Time.Clock ( UTCTime )
 import qualified Network.HTTP.Base as HTTP
 import qualified Network.HTTP.Headers as HTTP
 import           Text.Printf (printf)
@@ -746,7 +745,7 @@
 data PostQuery = PostQuery
   { postQueryPage    :: Maybe Int
   , postQueryPerPage :: Maybe Int
-  , postQuerySince   :: Maybe UTCTime
+  , postQuerySince   :: Maybe ServerTime
   , postQueryBefore  :: Maybe PostId
   , postQueryAfter   :: Maybe PostId
   }
@@ -765,7 +764,7 @@
   mkQueryString
     [ sequence ("page", fmap show postQueryPage)
     , sequence ("per_page", fmap show postQueryPerPage)
-    , sequence ("since", fmap show postQuerySince)
+    , sequence ("since", fmap (show . timeToServer) postQuerySince)
     , sequence ("before", fmap (T.unpack . idString) postQueryBefore)
     , sequence ("after", fmap (T.unpack . idString) postQueryAfter)
     ]