Keep yyyy-MM-dd for SimpleDateFormat, uuuu-MM-dd only for DateTimeFormatter

Co-authored-by: brunoborges <129743+brunoborges@users.noreply.github.com>

Author: Copilot

data/snippets.json

@@ -2424,7 +2424,7 @@
     "modernLabel": "Java 8+",
     "oldApproach": "SimpleDateFormat",
     "modernApproach": "DateTimeFormatter",
-    "oldCode": "// Not thread-safe!\nSimpleDateFormat sdf =\n    new SimpleDateFormat(\"uuuu-MM-dd\");\nString formatted = sdf.format(date);\n// Must synchronize for concurrent use",
+    "oldCode": "// Not thread-safe!\nSimpleDateFormat sdf =\n    new SimpleDateFormat(\"yyyy-MM-dd\");\nString formatted = sdf.format(date);\n// Must synchronize for concurrent use",
     "modernCode": "DateTimeFormatter fmt =\n    DateTimeFormatter.ofPattern(\n        \"uuuu-MM-dd\");\nString formatted =\n    LocalDate.now().format(fmt);\n// Thread-safe, immutable",
     "summary": "Format dates with thread-safe, immutable DateTimeFormatter.",
     "explanation": "DateTimeFormatter is immutable and thread-safe, unlike SimpleDateFormat. It can be stored as a constant and shared. Predefined formatters like ISO_LOCAL_DATE are available for common formats.",

date-formatting.html

@@ -125,7 +125,7 @@ <h1>Date formatting</h1>
           <div class="compare-code">
             <pre class="code-text">// Not thread-safe!
 SimpleDateFormat sdf =
-    new SimpleDateFormat(&quot;uuuu-MM-dd&quot;);
+    new SimpleDateFormat(&quot;yyyy-MM-dd&quot;);
 String formatted = sdf.format(date);
 // Must synchronize for concurrent use</pre>
           </div>

duration-and-period.html

@@ -254,7 +254,7 @@ <h3>Date formatting</h3>
               <div class="mini-label">Pre-Java 8</div>
               <pre class="code-text">// Not thread-safe!
 SimpleDateFormat sdf =
-    new SimpleDateFormat(&quot;uuuu-MM-dd&quot;);
+    new SimpleDateFormat(&quot;yyyy-MM-dd&quot;);
 String formatted = sdf.format(date);
 // Must synchronize for concurrent use</pre>
             </div>

hex-format.html

@@ -220,7 +220,7 @@ <h3>Date formatting</h3>
               <div class="mini-label">Pre-Java 8</div>
               <pre class="code-text">// Not thread-safe!
 SimpleDateFormat sdf =
-    new SimpleDateFormat(&quot;uuuu-MM-dd&quot;);
+    new SimpleDateFormat(&quot;yyyy-MM-dd&quot;);
 String formatted = sdf.format(date);
 // Must synchronize for concurrent use</pre>
             </div>

index.html

@@ -2516,7 +2516,7 @@ <h3>Date formatting</h3>
             <span class="mini-label">Old</span>
             <span class="code-text">// Not thread-safe!
 SimpleDateFormat sdf =
-    new SimpleDateFormat(&quot;uuuu-MM-dd&quot;);
+    new SimpleDateFormat(&quot;yyyy-MM-dd&quot;);
 String formatted = sdf.format(date);
 // Must synchronize for concurrent use</span>
           </div>

java-time-basics.html

@@ -286,7 +286,7 @@ <h3>Date formatting</h3>
               <div class="mini-label">Pre-Java 8</div>
               <pre class="code-text">// Not thread-safe!
 SimpleDateFormat sdf =
-    new SimpleDateFormat(&quot;uuuu-MM-dd&quot;);
+    new SimpleDateFormat(&quot;yyyy-MM-dd&quot;);
 String formatted = sdf.format(date);
 // Must synchronize for concurrent use</pre>
             </div>