diff --git a/lib/ctt/__init__.py b/lib/ctt/__init__.py
index ea1c6fd..3d008a0 100644
--- a/lib/ctt/__init__.py
+++ b/lib/ctt/__init__.py
@@ -27,9 +27,13 @@ VERSION         = "0.1"
 FILE_DELTA      = "delta"
 DATEFORMAT      = "%Y-%m-%d"
 DATEFORMAT_PLAIN= DATEFORMAT.replace("%","")
-DATETIMEFORMAT      = "%Y-%m-%d-%H:%M"
+DATETIMEFORMAT      = "%Y-%m-%d-%H%M"
 DATETIMEFORMAT_PLAIN= DATETIMEFORMAT.replace("%","")
 
+# Name of the folder to create - should not contain special characters
+# to ensure cross-os compatibility
+DISKFORMAT      = DATETIMEFORMAT
+
 class Error(Exception):
     pass
 
diff --git a/lib/ctt/report.py b/lib/ctt/report.py
index c2ebee3..241d112 100755
--- a/lib/ctt/report.py
+++ b/lib/ctt/report.py
@@ -74,15 +74,15 @@ class Report(object):
 
         self._report_db = {}
         for dirname in os.listdir(self.project_dir):
-            if dirname >= self.start_seconds and dirname <= self.end_seconds:
+            dir_datetime = datetime.datetime.strptime(dirname, ctt.DISKFORMAT)
+            if dir_datetime >= self.start_date and dir_datetime <= self.end_date:
                 filename = os.path.join(self.project_dir, dirname, ctt.FILE_DELTA)
                 with open(filename, "r") as fd:
                     self._report_db[dirname] = fd.read().rstrip('\n')
 
-                log.debug("%s: %s" % (dirname, self._report_db[dirname]))
+                log.debug("Recording: %s: %s" % (dirname, self._report_db[dirname]))
             else:
-                log.debug("%s/%s" % (float(dirname) - float(self.start_seconds), 
-                    float(self.end_seconds) - float(dirname)))
+                log.debug("Skipping: %s" % dirname)
 
     def report(self):
         """Show report to the user"""
diff --git a/lib/ctt/tracker.py b/lib/ctt/tracker.py
index d765e95..8c72e73 100755
--- a/lib/ctt/tracker.py
+++ b/lib/ctt/tracker.py
@@ -93,11 +93,8 @@ class Tracker:
             raise ctt.Error("End date must be after start date! (%s > %s)!" %
                 (self.start_datetime, self.end_datetime))
 
-        start_seconds =  self.start_datetime.strftime("%s")
-        end_seconds =  self.end_datetime.strftime("%s")
-        delta_seconds = self.delta()
-
-        time_dir = os.path.join(self.project_dir, start_seconds)
+        subdirname = self.start_datetime.strftime(ctt.DISKFORMAT)
+        time_dir = os.path.join(self.project_dir, subdirname)
 
         if os.path.exists(time_dir):
             raise ctt.Error("Already tracked time at this beginning for this project")
@@ -106,7 +103,7 @@ class Tracker:
         filename = os.path.join(time_dir, ctt.FILE_DELTA)
 
         with open(filename, "w") as fd:
-            fd.write("%s\n" % delta_seconds)
+            fd.write("%s\n" % self.delta())
 
     def delta(self, in_seconds=True):
         """Return time delta - empty (==0) if not tracked"""
diff --git a/tools/convert-0.1-to-0.2-format b/tools/convert-0.1-to-0.2-format
new file mode 100755
index 0000000..c6cfc8c
--- /dev/null
+++ b/tools/convert-0.1-to-0.2-format
@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+
+import datetime
+import os
+import os.path
+
+DATETIMEFORMAT      = "%Y-%m-%d-%H%M"
+DISKFORMAT      = DATETIMEFORMAT
+
+
+basedir = os.environ['HOME']
+ctt_dir = os.path.join(basedir, ".ctt")
+
+for project in os.listdir(ctt_dir):
+    time_dir = os.path.join(ctt_dir, project)
+    for time in os.listdir(time_dir):
+        print("Converting dir %s/%s" % (project, time))
+        try:
+            import_time = datetime.datetime.fromtimestamp(int(time))
+        except ValueError as e:
+            print("No old style directory %s from project %s - skipping" % (time, project))
+            continue
+
+        new_dirname = import_time.strftime(DISKFORMAT)
+
+        print("%s -> %s" % (time, new_dirname))
+        src = os.path.join(ctt_dir, project, time)
+        dst = os.path.join(ctt_dir, project, new_dirname)
+        print("%s -> %s" % (src, dst))
+
+        if os.path.exists(dst):
+            print("Cannot overwrite dst: %s, skipping %s" % (dst, src))
+            continue
+
+        os.rename(src, dst)
+