diff --git a/backup.py b/backup.py
new file mode 100644
index 0000000..cd75962
--- /dev/null
+++ b/backup.py
@@ -0,0 +1,74 @@
+#!/usr/bin/env python
+# encoding: utf8
+
+import hashlib
+import json
+import os
+from datetime import datetime, timedelta
+
+from togglapi import api
+
+from config import API_TOKEN, TIMEZONE
+
+START_MONTH = '2015-03'
+
+
+def get_month_start(time):
+    return time.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
+
+
+def get_month_end(time):
+    month_start = get_month_start(time)
+    next_month_start = (month_start + timedelta(days=31)).replace(day=1)
+    return next_month_start - timedelta(seconds=1)
+
+
+def dump(dump_dir, year, month, verbose=False):
+    time = datetime(year=year, month=month, day=1)
+    month_start = get_month_start(time)
+    month_end = get_month_end(time)
+    month = '%d-%02d' % (year, month)
+    if verbose:
+        print month + ':',
+        print month_start.isoformat(), 'to', month_end.isoformat(), '...'
+    toggl = api.TogglAPI(API_TOKEN, TIMEZONE)
+    data = toggl.get_time_entries(month_start.isoformat(), month_end.isoformat())
+    content = json.dumps(data)
+    if not os.path.exists(dump_dir):
+        os.makedirs(dump_dir)
+    filename = os.path.join(dump_dir, '%s.json' % month)
+
+    def md5(string):
+        return hashlib.md5(string).digest()
+
+    if os.path.exists(filename) and md5(content) == md5(open(filename).read()):
+        if verbose:
+            print filename, 'not changed.'
+    else:
+        file(filename, 'w').write(content)
+        if verbose:
+            print filename, 'saved.'
+    return data
+
+
+def backup(backup_dir, verbose=False):
+    time = datetime.now()
+    while True:
+        month = '%d-%02d' % (time.year, time.month)
+        if month < START_MONTH:
+            break
+        dump(backup_dir, time.year, time.month, verbose=verbose)
+        prev_month = (time - timedelta(days=31)).replace(day=1)
+        time = prev_month
+
+if __name__ == '__main__':
+    import sys
+    if len(sys.argv) == 1:
+        print 'Usage: %s backup_dir [-v]' % sys.argv[0]
+        sys.exit(1)
+    try:
+        verbose = sys.argv[2] == '-v'
+    except:
+        verbose = False
+    backup_dir = sys.argv[1]
+    backup(backup_dir, verbose=verbose)