fix: Time::difference() DST bug

Fixed to not convert to UTC when the two time zones are the same.

Author: kenjis

system/I18n/TimeTrait.php

@@ -1069,8 +1069,21 @@ public function humanize()
      */
     public function difference($testTime, ?string $timezone = null)
     {
-        $testTime = $this->getUTCObject($testTime, $timezone);
-        $ourTime  = $this->getUTCObject($this);
+        if (is_string($testTime)) {
+            $timezone = ($timezone !== null) ? new DateTimeZone($timezone) : $this->timezone;
+            $testTime = new DateTime($testTime, $timezone);
+        } elseif ($testTime instanceof self) {
+            $testTime = $testTime->toDateTime();
+        }
+
+        assert($testTime instanceof DateTime);
+
+        if ($this->timezone->getOffset($this) !== $testTime->getTimezone()->getOffset($this)) {
+            $testTime = $this->getUTCObject($testTime, $timezone);
+            $ourTime  = $this->getUTCObject($this);
+        } else {
+            $ourTime = $this->toDateTime();
+        }
 
         return new TimeDifference($ourTime, $testTime);
     }

tests/system/I18n/TimeDifferenceTest.php

@@ -120,7 +120,7 @@ public function testHumanizeMonthsForward(): void
         $current = Time::parse('March 1, 2017', 'America/Chicago');
         $diff    = $current->difference('May 1, 2017', 'America/Chicago');
 
-        $this->assertSame('in 1 month', $diff->humanize('en'));
+        $this->assertSame('in 2 months', $diff->humanize('en'));
     }
 
     public function testHumanizeDaysSingle(): void
@@ -211,12 +211,20 @@ public function testHumanizeWeeksPlural(): void
         $this->assertSame('2 weeks ago', $diff->humanize('en'));
     }
 
-    public function testHumanizeWeeksForward(): void
+    public function testHumanizeWeeksForwardDST(): void
     {
         $current = Time::parse('March 10, 2017', 'America/Chicago');
         $diff    = $current->difference('March 18, 2017', 'America/Chicago');
 
-        $this->assertSame('in 1 week', $diff->humanize('en'));
+        $this->assertSame('in 2 weeks', $diff->humanize('en'));
+    }
+
+    public function testHumanizeWeeksForwardUTC(): void
+    {
+        $current = Time::parse('2017-03-10');
+        $diff    = $current->difference('2017-03-18');
+
+        $this->assertSame('in 2 weeks', $diff->humanize('en'));
     }
 
     public function testHumanizeNoDifference(): void
@@ -238,14 +246,14 @@ public function testGetterUTC(): void
         $this->assertNull($diff->nonsense);
     }
 
-    public function testGetterChicagoTime(): void
+    public function testGetterDST(): void
     {
         $current = Time::parse('March 10, 2017', 'America/Chicago');
         $diff    = $current->difference('March 18, 2017', 'America/Chicago');
 
         // Daylight Saving Time had begun since Sun, 12 Mar, 02:00.
-        $this->assertSame(7, $diff->getDays());
-        $this->assertSame(7, $diff->days);
+        $this->assertSame(8, $diff->getDays());
+        $this->assertSame(8, $diff->days);
 
         // The raw value does not take Daylight Saving Time into account.
         $this->assertSame(-8, (int) round($diff->getDays(true)));