diff --git a/persistit/core/src/main/java/com/persistit/Key.java b/persistit/core/src/main/java/com/persistit/Key.java
index 219c03275..440f627ab 100644
--- a/persistit/core/src/main/java/com/persistit/Key.java
+++ b/persistit/core/src/main/java/com/persistit/Key.java
@@ -1,5 +1,6 @@
 /**
  * Copyright 2005-2012 Akiban Technologies, Inc.
+ * Portions Copyrighted 2026 3A Systems, LLC.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -504,14 +505,19 @@ public enum Direction {
     public final static EdgeValue AFTER = new EdgeValue(true);
 
     /**
-     * The <code>java.text.SimpleDateFormat</code> used in formatting
+     * A thread-local <code>java.text.SimpleDateFormat</code> used in formatting
      * <code>Date</code>- valued keys in the {@link #decodeDisplayable} methods.
      * This format also governs the conversion of dates for the
      * <code>toString</code> method. This format provides millisecond resolution
      * so that the precise stored representation of a date used as a key can be
      * represented exactly, but readably, in the displayable version.
+     * <p>
+     * <code>SimpleDateFormat</code> is not thread-safe, so the instance is held
+     * in a {@link ThreadLocal}; call {@link ThreadLocal#get()} to obtain the
+     * per-thread formatter, e.g. <code>SDF.get().format(date)</code>.
      */
-    public final static SimpleDateFormat SDF = new SimpleDateFormat("yyyyMMddHHmmss.SSSZ");
+    public final static ThreadLocal<SimpleDateFormat> SDF = ThreadLocal
+            .withInitial(() -> new SimpleDateFormat("yyyyMMddHHmmss.SSSZ"));
 
     /**
      * Displayable prefix for boolean values (optional for input, implied and
@@ -3139,7 +3145,7 @@ else if (cl == Boolean.class) {
 
         else if (cl == Date.class) {
             Util.append(sb, PREFIX_DATE);
-            Util.append(sb, SDF.format(decodeDate()));
+            Util.append(sb, SDF.get().format(decodeDate()));
         }
 
         else if (cl == byte[].class) {
diff --git a/persistit/core/src/main/java/com/persistit/KeyParser.java b/persistit/core/src/main/java/com/persistit/KeyParser.java
index 3fc768a06..13c6561be 100644
--- a/persistit/core/src/main/java/com/persistit/KeyParser.java
+++ b/persistit/core/src/main/java/com/persistit/KeyParser.java
@@ -1,5 +1,6 @@
 /**
  * Copyright 2005-2012 Akiban Technologies, Inc.
+ * Portions Copyrighted 2026 3A Systems, LLC.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -293,7 +294,7 @@ else if (matchExactString("false"))
                     }
                 } else if (matchExactString(Key.PREFIX_DATE) || matchExactString(Key.PREFIX_DATE0)) {
                     if (matchNumber(true, true)) {
-                        key.append(Key.SDF.parse(_sb.toString()));
+                        key.append(Key.SDF.get().parse(_sb.toString()));
                         result = true;
                     }
                 } else if (matchExactString(Key.PREFIX_BYTE_ARRAY)) {
diff --git a/persistit/core/src/main/java/com/persistit/Value.java b/persistit/core/src/main/java/com/persistit/Value.java
index 7e7cdb172..5a5d05d2a 100644
--- a/persistit/core/src/main/java/com/persistit/Value.java
+++ b/persistit/core/src/main/java/com/persistit/Value.java
@@ -1,5 +1,6 @@
 /**
  * Copyright 2005-2012 Akiban Technologies, Inc.
+ * Portions Copyrighted 2026 3A Systems, LLC.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -1566,7 +1567,7 @@ private void appendDisplayable(final StringBuilder sb, final Object value, final
           sb.append("...");
       } else if (cl == Date.class) {
         appendParenthesizedFriendlyClassName(sb, cl);
-        sb.append(Key.SDF.format((Date) value));
+        sb.append(Key.SDF.get().format((Date) value));
       } else if (value instanceof Number) {
         sb.append('(');
         sb.append(className.startsWith("java.lang.") ? className.substring(10) : className);
diff --git a/persistit/ui/src/main/java/com/persistit/ui/ValueInspectorTreeNode.java b/persistit/ui/src/main/java/com/persistit/ui/ValueInspectorTreeNode.java
index 3eb835090..906f9d41a 100644
--- a/persistit/ui/src/main/java/com/persistit/ui/ValueInspectorTreeNode.java
+++ b/persistit/ui/src/main/java/com/persistit/ui/ValueInspectorTreeNode.java
@@ -1,5 +1,6 @@
 /**
  * Copyright 2005-2012 Akiban Technologies, Inc.
+ * Portions Copyrighted 2026 3A Systems, LLC.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -156,7 +157,7 @@ String displayable(final String fieldName, final Class type, final Object object
                 sb.append('\"');
             } else if (object instanceof Date) {
                 sb.append(" = ");
-                sb.append(Key.SDF.format((Date) object));
+                sb.append(Key.SDF.get().format((Date) object));
             } else if (type == Boolean.class || type == Byte.class || type == Short.class || type == Character.class
                     || type == Integer.class || type == Long.class || type == Float.class || type == Double.class
                     || type == BigInteger.class || type == BigDecimal.class) {