diff --git a/changelog b/changelog
--- a/changelog
+++ b/changelog
@@ -1,3 +1,8 @@
+pandoc-citeproc (0.12.2.1)
+
+  * Handle pseudo-months in CSL date-range (see #103).
+    Month 13 = season 1, 14 = 2, also 21 = 1, 22 = 2, ...
+
 pandoc-citeproc (0.12.2)
 
   * Improved parsing of raw dates.  First we attempt to parse them
@@ -19,7 +24,7 @@
     + We now only parse 'raw' if `date-parts` is empty or missing.
     + Code for parsing raw dates moved from Text.CSL.Eval.Date to
       Text.CSL.Reference.
-    + Use `literal` field if we can't parse data.
+    + Use `other` field if we can't parse data.
 
   * Support `all-names-with-initials` disambiguation.
 
diff --git a/pandoc-citeproc.cabal b/pandoc-citeproc.cabal
--- a/pandoc-citeproc.cabal
+++ b/pandoc-citeproc.cabal
@@ -1,5 +1,5 @@
 name:               pandoc-citeproc
-version:            0.12.2
+version:            0.12.2.1
 cabal-version:      >= 1.12
 synopsis:           Supports using pandoc with citeproc
 
diff --git a/src/Text/CSL/Reference.hs b/src/Text/CSL/Reference.hs
--- a/src/Text/CSL/Reference.hs
+++ b/src/Text/CSL/Reference.hs
@@ -132,7 +132,7 @@
             } deriving ( Show, Read, Eq, Typeable, Data, Generic )
 
 instance FromJSON RefDate where
-  parseJSON (Array v) =
+  parseJSON (Array v) = handlePseudoMonths <$>
      case fromJSON (Array v) of
           Success [y]     -> RefDate <$> parseJSON y <*>
                     pure "" <*> pure "" <*> pure "" <*> pure "" <*> pure False
@@ -142,6 +142,17 @@
                     pure "" <*> parseJSON d <*> pure "" <*> pure False
           Error e         -> fail $ "Could not parse RefDate: " ++ e
           _               -> fail "Could not parse RefDate"
+     where handlePseudoMonths r =
+              case unLiteral (month r) of
+                   "13" -> r{ month = mempty, season = Literal "1" }
+                   "14" -> r{ month = mempty, season = Literal "2" }
+                   "15" -> r{ month = mempty, season = Literal "3" }
+                   "16" -> r{ month = mempty, season = Literal "4" }
+                   "21" -> r{ month = mempty, season = Literal "1" }
+                   "22" -> r{ month = mempty, season = Literal "2" }
+                   "23" -> r{ month = mempty, season = Literal "3" }
+                   "24" -> r{ month = mempty, season = Literal "4" }
+                   _    -> r
   parseJSON (Object v) = RefDate <$>
               v .:? "year" .!= "" <*>
               v .:? "month" .!= "" <*>
@@ -178,11 +189,11 @@
     raw' <- v .:? "raw"
     dateParts <- v .:? "date-parts"
     circa' <- (v .: "circa" >>= parseBool) <|> pure False
-    season' <- (v .: "season") <|> pure mempty
+    season' <- v .:? "season"
     case dateParts of
          Just (Array xs) | not (isJust raw') && not (V.null xs)
                           -> mapM (fmap (setCirca circa' .
-                                        setSeason season') . parseJSON)
+                                     maybe id setSeason season') . parseJSON)
                              $ V.toList xs
          _ -> case raw' of
                   Nothing -> handleLiteral <$> parseJSON (Object v)
@@ -877,7 +888,10 @@
 
 isoDate :: P.Parser RefDate
 isoDate = P.try $ do
-  y <- P.many1 P.digit
+  y <- do
+    sign <- P.option "" (P.string "-")
+    rest <- P.count 4 P.digit
+    return $ sign ++ rest
   m' <- P.option Nothing $ Just <$> P.try (P.char '-' >> P.many1 P.digit)
   (m,s) <- case m' >>= safeRead of
                    Just (n::Int)
@@ -920,7 +934,7 @@
              Just (n::Int) | n >= 1 && n <= 31 -> return (show n)
              _ -> fail "Improper day"
   let pyear = P.many1 P.digit
-  let sep = P.oneOf ['-',' ','/',','] >> P.spaces
+  let sep = P.oneOf [' ','/',','] >> P.spaces
   let rangesep = P.try $ P.spaces >> P.char '-' >> P.spaces
   let refDate = RefDate mempty mempty mempty mempty mempty False
   let date = P.choice $ map P.try [