diff --git a/animatplot/animation.py b/animatplot/animation.py
index 24f847a..ce19522 100644
--- a/animatplot/animation.py
+++ b/animatplot/animation.py
@@ -1,6 +1,8 @@
 from matplotlib.animation import FuncAnimation, PillowWriter
 from matplotlib.widgets import Button, Slider
 import matplotlib.pyplot as plt
+import numpy as np
+
 from animatplot import Timeline
 
 
@@ -95,7 +97,7 @@ def pause(event):
             self._pause ^= True
         self.button.on_clicked(pause)
 
-    def timeline_slider(self, text='Time', ax=None, valfmt='%1.2f', color=None):
+    def timeline_slider(self, text='Time', ax=None, valfmt=None, color=None):
         """Creates a timeline slider.
 
         Parameters
@@ -106,7 +108,7 @@ def timeline_slider(self, text='Time', ax=None, valfmt='%1.2f', color=None):
             The matplotlib axes to attach the slider to.
         valfmt : str, optional
             a format specifier used to print the time
-            Defaults to '%1.2f'
+            Defaults to '%s' for datetime64, timedelta64 and '%1.2f' otherwise.
         color :
             The color of the slider.
         """
@@ -119,6 +121,13 @@ def timeline_slider(self, text='Time', ax=None, valfmt='%1.2f', color=None):
         else:
             self.slider_ax = ax
 
+        if valfmt is None:
+            if (np.issubdtype(self.timeline.t.dtype, np.datetime64)
+               or np.issubdtype(self.timeline.t.dtype, np.timedelta64)):
+                valfmt = '%s'
+            else:
+                valfmt = '%1.2f'
+
         if self.timeline.log:
             valfmt = '$10^{%s}$' % valfmt