diff --git a/git-filter-repo b/git-filter-repo
index 628e702..de1f914 100755
--- a/git-filter-repo
+++ b/git-filter-repo
@@ -25,7 +25,8 @@ import textwrap
 from datetime import tzinfo, timedelta, datetime
 
 __all__ = ["Blob", "Reset", "FileChanges", "Commit", "Tag", "Progress",
-           "Checkpoint", "FastExportFilter", "FixedTimeZone", "ProgressWriter",
+           "Checkpoint", "FastExportFilter", "ProgressWriter",
+           "string_to_date", "date_to_string",
            "record_id_rename", "GitUtils", "FilteringOptions", "RepoFilter"]
 
 
@@ -36,15 +37,6 @@ def _timedelta_to_seconds(delta):
   offset = delta.days*86400 + delta.seconds + (delta.microseconds+0.0)/1000000
   return round(offset)
 
-def _write_date(file_, date):
-  """
-  Writes a date to a file. The file should already be open. The date is
-  written as seconds-since-epoch followed by the name of the timezone.
-  """
-  epoch = datetime.fromtimestamp(0, date.tzinfo)
-  file_.write('%d %s' % (_timedelta_to_seconds(date - epoch),
-                         date.tzinfo.tzname(0)))
-
 class FixedTimeZone(tzinfo):
   """
   Fixed offset in minutes east from UTC.
@@ -52,21 +44,7 @@ class FixedTimeZone(tzinfo):
 
   def __init__(self, offset_string):
     tzinfo.__init__(self)
-    try:
-      sign, hh, mm = re.match(r'^([-+]?)(\d\d)(\d\d)$', offset_string).groups()
-    except AttributeError:
-      # TimeZone idiocy; IST is any of four timezones, so someone translated
-      # it to something that was totally invalid...and it got recorded that
-      # way.  Others have suggested just using an invalid timezone that
-      # fast-import will not choke on.  Let's do that.  Note that +051800
-      # seems to be the only weird timezone found in the wild, by me or some
-      # other posts google returned on the subject...
-      if offset_string == '+051800':
-        sign, hh, mm = '+', '02', '61'
-        offset_string = offset_string.replace('+051800', '+0261')
-      else:
-        raise AttributeError("Could not parse {} as timezone"
-                             .format(offset_string))
+    sign, hh, mm = re.match(r'^([-+]?)(\d\d)(\d\d)$', offset_string).groups()
     factor = -1 if (sign and sign == '-') else 1
     self._offset = timedelta(minutes = factor*(60*int(hh) + int(mm)))
     self._offset_string = offset_string
@@ -80,6 +58,16 @@ class FixedTimeZone(tzinfo):
   def dst(self, dt):
     return timedelta(0)
 
+def string_to_date(datestring):
+  (unix_timestamp, tz_offset) = datestring.split()
+  return datetime.fromtimestamp(int(unix_timestamp),
+                                FixedTimeZone(tz_offset))
+
+def date_to_string(dateobj):
+  epoch = datetime.fromtimestamp(0, dateobj.tzinfo)
+  return('{} {}'.format(int(_timedelta_to_seconds(dateobj - epoch)),
+                        dateobj.tzinfo.tzname(0)))
+
 class PathQuoting:
   _unescape = {'a': '\a',
                'b': '\b',
@@ -601,11 +589,11 @@ class Commit(_GitElementWithId):
     file_.write('commit %s\n' % self.branch)
     file_.write('mark :%d\n' % self.id)
     file_.write('author %s <%s> ' % (self.author_name, self.author_email))
-    _write_date(file_, self.author_date)
+    file_.write(self.author_date)
     file_.write('\n')
     file_.write('committer %s <%s> ' % \
                      (self.committer_name, self.committer_email))
-    _write_date(file_, self.committer_date)
+    file_.write(self.committer_date)
     file_.write('\n')
     file_.write('data %d\n%s' % (len(self.message), self.message))
     if not self.message.endswith("\n"):
@@ -689,7 +677,7 @@ class Tag(_GitElement):
     file_.write('from {}{}\n'.format(mark, self.from_ref))
     if self.tagger_name:
       file_.write('tagger %s <%s> ' % (self.tagger_name, self.tagger_email))
-      _write_date(file_, self.tagger_date)
+      file_.write(self.tagger_date)
       file_.write('\n')
     file_.write('data %d\n%s' % (len(self.tag_message), self.tag_message))
     file_.write('\n')
@@ -980,13 +968,17 @@ class FastExportFilter(object):
       re.match('%s (.*?) <(.*?)> (.*)\n$' %
                usertype, self._currentline).groups()
 
-    # Translate when into a datetime object, with corresponding timezone info
-    (unix_timestamp, tz_offset) = when.split()
-    datestamp = datetime.fromtimestamp(int(unix_timestamp),
-                                       FixedTimeZone(tz_offset))
+    # TimeZone idiocy; IST is any of four timezones, so someone translated
+    # it to something that was totally invalid...and it got recorded that
+    # way.  Others have suggested just using an invalid timezone that
+    # fast-import will not choke on.  Let's do that.  Note that +051800
+    # seems to be the only weird timezone found in the wild, by me or some
+    # other posts google returned on the subject...
+    if when.endswith('+051800'):
+      when = when[0:-7]+'+0261'
 
     self._advance_currentline()
-    return (name, email, datestamp)
+    return (name, email, when)
 
   def _parse_data(self):
     """
diff --git a/t/t9391/commit_info.py b/t/t9391/commit_info.py
index 673f18e..71a5dfe 100755
--- a/t/t9391/commit_info.py
+++ b/t/t9391/commit_info.py
@@ -26,7 +26,9 @@ def change_up_them_commits(commit):
   commit.author_email = re.sub("@my.crp", "@my.corp", commit.author_email)
 
   # Fix the committer date (bad timezone conversion in initial import)
-  commit.committer_date += timedelta(hours=-5)
+  oldtime = repo_filter.string_to_date(commit.committer_date)
+  newtime = oldtime + timedelta(hours=-5)
+  commit.committer_date = repo_filter.date_to_string(newtime)
 
   # Fix the commit message
   commit.message = re.sub("Marketing is staffed with pansies", "",
diff --git a/t/t9391/create_fast_export_output.py b/t/t9391/create_fast_export_output.py
index fe055bc..1b99db2 100755
--- a/t/t9391/create_fast_export_output.py
+++ b/t/t9391/create_fast_export_output.py
@@ -36,9 +36,10 @@ changes = [FileChanges('M', 'world', world.id, mode="100644"),
 when = datetime(year=2005, month=4, day=7,
                 hour=15, minute=16, second=10,
                 tzinfo=FixedTimeZone("-0700"))
+when_string = repo_filter.date_to_string(when)
 commit1 = Commit("refs/heads/master",
-                 "A U Thor", "au@thor.email", when,
-                 "Com M. Iter", "comm@iter.email", when,
+                 "A U Thor", "au@thor.email", when_string,
+                 "Com M. Iter", "comm@iter.email", when_string,
                  "My first commit!  Wooot!\n\nLonger description",
                  changes,
                  from_commit = None,
@@ -53,9 +54,10 @@ world_link.dump(output)
 changes = [FileChanges('M', 'world',  world.id,      mode="100644"),
            FileChanges('M', 'planet', world_link.id, mode="120000")]
 when += timedelta(days=3, hours=4, minutes=6)
+when_string = repo_filter.date_to_string(when)
 commit2 = Commit("refs/heads/master",
-                 "A U Thor", "au@thor.email", when,
-                 "Com M. Iter", "comm@iter.email", when,
+                 "A U Thor", "au@thor.email", when_string,
+                 "Com M. Iter", "comm@iter.email", when_string,
                  "Make a symlink to world called planet, modify world",
                  changes,
                  from_commit = commit1.id,
@@ -66,10 +68,10 @@ script = Blob("#!/bin/sh\n\necho Hello")
 script.dump(output)
 changes = [FileChanges('M', 'runme', script.id, mode="100755"),
            FileChanges('D', 'bar')]
-when = datetime.fromtimestamp(timestamp=1234567890, tz=FixedTimeZone("-0700"))
+when_string = "1234567890 -0700"
 commit3 = Commit("refs/heads/master",
-                 "A U Thor", "au@thor.email", when,
-                 "Com M. Iter", "comm@iter.email", when,
+                 "A U Thor", "au@thor.email", when_string,
+                 "Com M. Iter", "comm@iter.email", when_string,
                  "Add runme script, remove bar",
                  changes,
                  from_commit = commit2.id,
@@ -89,9 +91,10 @@ world.dump(output)
 
 changes = [FileChanges('M', 'world', world.id, mode="100644")]
 when = datetime(2006, 8, 17, tzinfo=FixedTimeZone("+0200"))
+when_string = repo_filter.date_to_string(when)
 commit4 = Commit("refs/heads/devel",
-                 "A U Thor", "au@thor.email", when,
-                 "Com M. Iter", "comm@iter.email", when,
+                 "A U Thor", "au@thor.email", when_string,
+                 "Com M. Iter", "comm@iter.email", when_string,
                  "Modify world",
                  changes,
                  from_commit = commit1.id,
@@ -100,7 +103,8 @@ commit4.dump(output)
 
 world = Blob("Hello\nHi\nGoodbye")
 world.dump(output)
-when = commit3.author_date + timedelta(days=47)
+when = repo_filter.string_to_date(commit3.author_date) + timedelta(days=47)
+when_string = repo_filter.date_to_string(when)
 # git fast-import requires file changes to be listed in terms of differences
 # to the first parent.  Thus, despite the fact that runme and planet have
 # not changed and bar was not modified in the devel side, we have to list them
@@ -111,8 +115,8 @@ changes = [FileChanges('M', 'world', world.id, mode="100644"),
            FileChanges('M', 'planet', world_link.id, mode="120000")]
 
 commit5 = Commit("refs/heads/devel",
-                 "A U Thor", "au@thor.email", when,
-                 "Com M. Iter", "comm@iter.email", when,
+                 "A U Thor", "au@thor.email", when_string,
+                 "Com M. Iter", "comm@iter.email", when_string,
                  "Merge branch 'master'\n",
                  changes,
                  from_commit = commit4.id,
@@ -121,7 +125,7 @@ commit5.dump(output)
 
 
 mytag = Tag("refs/tags/v1.0", commit5.id,
-            "His R. Highness", "royalty@my.kingdom", when,
+            "His R. Highness", "royalty@my.kingdom", when_string,
             "I bequeath to my peons this royal software")
 mytag.dump(output)
 out.finish()