diff --git a/petl/util/random.py b/petl/util/random.py
index 94fa7588..804b36ec 100644
--- a/petl/util/random.py
+++ b/petl/util/random.py
@@ -1,6 +1,5 @@
 from __future__ import absolute_import, print_function, division
 
-
 import datetime
 import random
 import time
@@ -8,7 +7,6 @@
 from functools import partial
 from petl.compat import xrange, text_type
 
-
 from petl.util.base import Table
 
 
@@ -52,7 +50,7 @@ def __init__(self, numflds=5, numrows=100, wait=0, seed=None):
         self.numrows = numrows
         self.wait = wait
         if seed is None:
-            self.seed = datetime.datetime.now()
+            self.seed = datetime.datetime.now().isoformat()
         else:
             self.seed = seed
 
@@ -77,7 +75,7 @@ def __iter__(self):
             yield tuple(random.random() for n in range(nf))
 
     def reseed(self):
-        self.seed = datetime.datetime.now()
+        self.seed = datetime.datetime.now().isoformat()
 
 
 def dummytable(numrows=100,
@@ -154,7 +152,7 @@ def __init__(self, numrows=100, fields=None, wait=0, seed=None):
         else:
             self.fields = OrderedDict(fields)
         if seed is None:
-            self.seed = datetime.datetime.now()
+            self.seed = datetime.datetime.now().isoformat()
         else:
             self.seed = seed
 
@@ -181,4 +179,4 @@ def __iter__(self):
             yield tuple(fields[f]() for f in fields)
 
     def reseed(self):
-        self.seed = datetime.datetime.now()
+        self.seed = datetime.datetime.now().isoformat()