docs: add timezone to the timestamp example so readers can see the output depends on their server's timezone

Author: daveedis

docs/text-and-formatting.md

@@ -142,11 +142,11 @@ echo $date->dateFormat();  // May 15th, 2026
 ```
 
 There is one method for dates and datetimes; the format string decides what
-shows. Numeric values are treated as unix timestamps; everything else is
-parsed with `strtotime()`:
+shows. Numeric values are treated as unix timestamps and format in your
+server's PHP timezone; everything else is parsed with `strtotime()`:
 
 ```php
-echo SmartString::new(1684159800)->dateFormat('Y-m-d');  // 2023-05-15
+echo SmartString::new(1684159800)->dateFormat('Y-m-d T');  // 2023-05-15 PDT
 ```
 
 Invalid dates return null rather than throwing, so a fallback chains

tests/Integration/DocsExamplesTest.php

@@ -244,7 +244,8 @@ public function testDateFormat(): void
         SmartString::$dateFormat = 'F jS, Y';
         $this->assertSame('May 15th, 2026', (string)$date->dateFormat());
 
-        $this->assertSame('2023-05-15', (string)SmartString::new(1684159800)->dateFormat('Y-m-d'));
+        date_default_timezone_set('America/Vancouver'); // the docs show the timestamp example with T = PDT
+        $this->assertSame('2023-05-15 PDT', (string)SmartString::new(1684159800)->dateFormat('Y-m-d T'));
 
         $invalid = SmartString::new("not a date");
         $this->assertSame('Date not set', (string)$invalid->dateFormat()->or("Date not set"));