diff --git a/openmc/mgxs/library.py b/openmc/mgxs/library.py
index 9add7004bb..ed8e3f076c 100644
--- a/openmc/mgxs/library.py
+++ b/openmc/mgxs/library.py
@@ -587,7 +587,7 @@ class Library(object):
         self._nuclides = statepoint.summary.nuclides
 
         if statepoint.run_mode == 'eigenvalue':
-            self._keff = statepoint.k_combined[0]
+            self._keff = statepoint.k_combined.n
 
         # Load tallies for each MGXS for each domain and mgxs type
         for domain in self.domains:
diff --git a/openmc/model/model.py b/openmc/model/model.py
index cd51533217..7a81292c1a 100644
--- a/openmc/model/model.py
+++ b/openmc/model/model.py
@@ -210,7 +210,7 @@ class Model(object):
 
         Returns
         -------
-        2-tuple of float
+        uncertainties.UFloat
             Combined estimator of k-effective from the statepoint
 
         """
diff --git a/openmc/search.py b/openmc/search.py
index 75935097e4..6be8a50ea5 100644
--- a/openmc/search.py
+++ b/openmc/search.py
@@ -60,9 +60,9 @@ def _search_keff(guess, target, model_builder, model_args, print_iterations,
     if print_iterations:
         text = 'Iteration: {}; Guess of {:.2e} produced a keff of ' + \
             '{:1.5f} +/- {:1.5f}'
-        print(text.format(len(guesses), guess, keff[0], keff[1]))
+        print(text.format(len(guesses), guess, keff.n, keff.s))
 
-    return (keff[0] - target)
+    return keff.n - target
 
 
 def search_for_keff(model_builder, initial_guess=None, target=1.0,
diff --git a/openmc/statepoint.py b/openmc/statepoint.py
index 4656e08560..eb011d8742 100644
--- a/openmc/statepoint.py
+++ b/openmc/statepoint.py
@@ -1,3 +1,4 @@
+from datetime import datetime
 import re
 import os
 import warnings
@@ -5,6 +6,7 @@ import glob
 
 import numpy as np
 import h5py
+from uncertainties import ufloat
 
 import openmc
 import openmc.checkvalue as cv
@@ -47,8 +49,8 @@ class StatePoint(object):
         CMFD fission source distribution over all mesh cells and energy groups.
     current_batch : int
         Number of batches simulated
-    date_and_time : str
-        Date and time when simulation began
+    date_and_time : datetime.datetime
+        Date and time at which statepoint was written
     entropy : numpy.ndarray
         Shannon entropy of fission source at each batch
     filters : dict
@@ -59,8 +61,8 @@ class StatePoint(object):
     global_tallies : numpy.ndarray of compound datatype
         Global tallies for k-effective estimates and leakage. The compound
         datatype has fields 'name', 'sum', 'sum_sq', 'mean', and 'std_dev'.
-    k_combined : list
-        Combined estimator for k-effective and its uncertainty
+    k_combined : uncertainties.UFloat
+        Combined estimator for k-effective
     k_col_abs : float
         Cross-product of collision and absorption estimates of k-effective
     k_col_tra : float
@@ -187,7 +189,8 @@ class StatePoint(object):
 
     @property
     def date_and_time(self):
-        return self._f.attrs['date_and_time'].decode()
+        s = self._f.attrs['date_and_time'].decode()
+        return datetime.strptime(s, '%Y-%m-%d %H:%M:%S')
 
     @property
     def entropy(self):
@@ -255,7 +258,7 @@ class StatePoint(object):
     @property
     def k_combined(self):
         if self.run_mode == 'eigenvalue':
-            return self._f['k_combined'].value
+            return ufloat(*self._f['k_combined'].value)
         else:
             return None
 
@@ -457,7 +460,7 @@ class StatePoint(object):
 
     @property
     def version(self):
-        return tuple(self._f.attrs['version'])
+        return tuple(self._f.attrs['openmc_version'])
 
     @property
     def summary(self):
diff --git a/tests/regression_tests/entropy/test.py b/tests/regression_tests/entropy/test.py
index 0f1052b6b8..10a11e3008 100644
--- a/tests/regression_tests/entropy/test.py
+++ b/tests/regression_tests/entropy/test.py
@@ -14,11 +14,11 @@ class EntropyTestHarness(TestHarness):
         with StatePoint(statepoint) as sp:
             # Write out k-combined.
             outstr = 'k-combined:\n'
-            outstr += '{0:12.6E} {1:12.6E}\n'.format(*sp.k_combined)
+            outstr += '{:12.6E} {:12.6E}\n'.format(sp.k_combined.n, sp.k_combined.s)
 
             # Write out entropy data.
             outstr += 'entropy:\n'
-            results = ['{0:12.6E}'.format(x) for x in sp.entropy]
+            results = ['{:12.6E}'.format(x) for x in sp.entropy]
             outstr += '\n'.join(results) + '\n'
 
         return outstr
diff --git a/tests/regression_tests/mg_convert/test.py b/tests/regression_tests/mg_convert/test.py
index 5b816a1cd0..1ace10c80b 100755
--- a/tests/regression_tests/mg_convert/test.py
+++ b/tests/regression_tests/mg_convert/test.py
@@ -144,8 +144,8 @@ class MGXSTestHarness(PyAPITestHarness):
             with openmc.StatePoint('statepoint.{}.h5'.format(batches)) as sp:
                 # Write out k-combined.
                 outstr += 'k-combined:\n'
-                form = '{0:12.6E} {1:12.6E}\n'
-                outstr += form.format(sp.k_combined[0], sp.k_combined[1])
+                form = '{:12.6E} {:12.6E}\n'
+                outstr += form.format(sp.k_combined.n, sp.k_combined.s)
 
         return outstr
 
diff --git a/tests/testing_harness.py b/tests/testing_harness.py
index 92d477e238..fb07575ce7 100644
--- a/tests/testing_harness.py
+++ b/tests/testing_harness.py
@@ -75,7 +75,7 @@ class TestHarness(object):
             # Write out k-combined.
             outstr = 'k-combined:\n'
             form = '{0:12.6E} {1:12.6E}\n'
-            outstr += form.format(sp.k_combined[0], sp.k_combined[1])
+            outstr += form.format(sp.k_combined.n, sp.k_combined.s)
 
             # Write out tally data.
             for i, tally_ind in enumerate(sp.tallies):