diff --git a/fix-copyright.py b/fix-copyright.py
new file mode 100755
index 0000000..f484822
--- /dev/null
+++ b/fix-copyright.py
@@ -0,0 +1,71 @@
+#!/usr/bin/env python
+from subprocess import check_output as run
+from datetime import datetime
+from itertools import groupby
+from operator import itemgetter
+import re
+import magic
+
+def authors(filename):
+    log = run(['git', 'log', '--follow',
+              '--date=short','--format=%aN%x09%ad', filename],
+              universal_newlines=True)
+    for line in log.splitlines():
+        author, date = line.split('\t')
+        if author != 'fix-copyright.py':
+            yield author, datetime.strptime(date, '%Y-%m-%d')
+
+def new_copyright(filename, previous):
+    def f():
+        au = list(authors(filename))
+        alldates = map(itemgetter(1), au)
+        aup = sorted(au + map(lambda a: (a, None), previous), key=itemgetter(0))
+        for author, records in groupby(aup, itemgetter(0)):
+            dates = filter(None, map(itemgetter(1), records))
+            if not dates: dates = alldates
+            start = min(dates)
+            end = max(dates)
+            fmt = '{0}' if start.year == end.year else '{0}-{1}'
+            line = 'Copyright ' + fmt.format(start.year, end.year) + ' ' + author
+            key = (start, author)
+            yield key, line
+    return map(itemgetter(1), sorted(f()))
+
+def fix_copyright(filename):
+    # Find copyright block in original file
+    prefix = set()
+    names = []
+    lines = []
+    with open(filename, 'r') as f:
+        content = list(f)
+    for i, line in enumerate(content[:15]):
+        m = re.match(r'^(?P<prefix>\W*)(\(c\))?\s*?copyright\s*(\(c\))?\s+\d{4}(\s*-\s*\d{4})?\s+(?P<name>.+?)\s*$', line, re.IGNORECASE)
+        if m:
+            d = m.groupdict()
+            prefix.add(d['prefix'])
+            lines.append(i)
+            names.append(d['name'].strip())
+    if len(prefix) != 1:
+        print 'Not found:', filename
+        return
+    prefix = list(prefix)[0]
+
+    print filename
+    new = iter(new_copyright(filename, names))
+    with open(filename, 'w') as f:
+        for i, line in enumerate(content):
+            if i in lines:
+                for repl in new:
+                    print >>f, prefix + repl
+            else:
+                print >>f, line,
+    pass
+
+def all_files():
+    ls = run(['git', 'ls-files'], universal_newlines=True)
+    for filename in ls.splitlines():
+        if magic.from_file(filename, mime=True).split('/')[0] == 'text':
+            yield filename
+
+for f in all_files():
+    fix_copyright(f)