diff --git a/Version.hs b/Version.hs
new file mode 100644
--- /dev/null
+++ b/Version.hs
@@ -0,0 +1,41 @@
+-- boilerplate {{{
+module Version (CurrentFormat, parseCurrentFormat, version) where
+import Data.Map (Map, elems, empty)
+import Data.Time (UTCTime, getCurrentTime)
+
+type CurrentFormat = FormatV2
+version            :: String
+parseCurrentFormat :: String -> IO CurrentFormat
+
+version            = "yeganesh version 2.2.1"
+parseCurrentFormat = parseFormatV2
+-- }}}
+-- v2 {{{
+type FormatV2 = (UTCTime, FormatV1)
+
+parseFormatV2 :: String -> IO FormatV2
+parseFormatV2 = parse parseFormatV1 upgradeFormatV1
+-- }}}
+-- v1 {{{
+type FormatV1 = Map String Double
+
+upgradeFormatV1 :: FormatV1 -> IO FormatV2
+upgradeFormatV1 v1 = fmap (flip (,) popularities) getCurrentTime where
+    maximal = case (elems v1, maximum (elems v1)) of
+        ([], _) -> 1
+        (_ , 0) -> 1
+        (_ , m) -> m
+    popularities = fmap (/maximal) v1
+
+parseFormatV1 :: String -> IO FormatV1
+parseFormatV1 = parse (const (return empty)) return
+-- }}}
+-- utilities {{{
+parse :: Read new => (String -> IO old) -> (old -> IO new) -> (String -> IO new)
+parse old upgrade s = maybe (old s >>= upgrade) return (readMaybe s)
+
+readMaybe :: Read a => String -> Maybe a
+readMaybe s = case reads s of
+    [(x, "")] -> Just x
+    _         -> Nothing
+-- }}}
diff --git a/yeganesh.cabal b/yeganesh.cabal
--- a/yeganesh.cabal
+++ b/yeganesh.cabal
@@ -1,5 +1,5 @@
 name:               yeganesh
-version:            2.2
+version:            2.2.1
 cabal-version:      >=1.2
 build-type:         Simple
 license:            BSD3
@@ -12,10 +12,11 @@
                     programs I use every day aren't at the beginning of the
                     list.  Let's make it so, and automatically!
 category:           Text
+extra-source-files: Version.hs
 
 Executable yeganesh
     main-is:        yeganesh.hs
-    build-depends:  base >= 3 && <= 4,
+    build-depends:  base >= 3 && < 5,
                     containers >= 0.1,
                     directory >= 1.0,
                     filepath >= 1.1,