diff --git a/pyexcel_xls/xlsw.py b/pyexcel_xls/xlsw.py
index c07a9b3..4822cd3 100644
--- a/pyexcel_xls/xlsw.py
+++ b/pyexcel_xls/xlsw.py
@@ -16,6 +16,7 @@ from pyexcel_io.plugin_api import IWriter, ISheetWriter
 
 DEFAULT_DATE_FORMAT = "DD/MM/YY"
 DEFAULT_TIME_FORMAT = "HH:MM:SS"
+DEFAULT_LONGTIME_FORMAT = "[HH]:MM:SS"
 DEFAULT_DATETIME_FORMAT = "%s %s" % (DEFAULT_DATE_FORMAT, DEFAULT_TIME_FORMAT)
 EMPTY_SHEET_NOT_ALLOWED = "xlwt does not support a book without any sheets"
 
@@ -53,13 +54,9 @@ class XLSheetWriter(ISheetWriter):
                 style = XFStyle()
                 style.num_format_str = DEFAULT_DATETIME_FORMAT
             elif isinstance(value, datetime.timedelta):
-                hours = value.days * 24 + value.seconds // 3600
-                minutes = (value.seconds // 60) % 60
-                seconds = value.seconds % 60
-                tmp_array = [hours, minutes, seconds]
-                value = xlrd.xldate.xldate_from_time_tuple(tmp_array)
+                value = value.days + value.seconds / 86_400
                 style = XFStyle()
-                style.num_format_str = DEFAULT_TIME_FORMAT
+                style.num_format_str = DEFAULT_LONGTIME_FORMAT
             elif isinstance(value, datetime.date):
                 tmp_array = [value.year, value.month, value.day]
                 value = xlrd.xldate.xldate_from_date_tuple(tmp_array, 0)
diff --git a/tests/test_formatters.py b/tests/test_formatters.py
index e87a017..a3c7518 100644
--- a/tests/test_formatters.py
+++ b/tests/test_formatters.py
@@ -56,8 +56,8 @@ class TestDateFormat:
         assert r[0, 1].strftime("%H:%M:%S") == "11:11:11"
         assert isinstance(r[0, 2], datetime.date) is True
         assert r[0, 2].strftime("%d/%m/%y %H:%M:%S") == "25/12/14 11:11:11"
-        assert isinstance(r[0, 2], datetime.timedelta)
-        assert r[0, 1].strftime("%H:%M:%S") == "3:30:20"
+        assert isinstance(r[0, 3], datetime.datetime)
+        assert r[0, 3].strftime("%D-%H:%M:%S") == "03/04/00-08:05:56"
         os.unlink(excel_filename)