test(compare): trace deterministic monthly seed progression

src/sammo/TimeUtil.php

@@ -7,6 +7,19 @@ use phpDocumentor\Reflection\Types\Boolean;
 class TimeUtil
 {
 
+    private static function comparisonNow(): ?\DateTimeImmutable
+    {
+        $comparisonNow = getenv('REF_COMPARISON_NOW');
+        if (
+            getenv('REF_DETERMINISTIC_INSTALL_ENABLED') !== '1'
+            || !is_string($comparisonNow)
+            || $comparisonNow === ''
+        ) {
+            return null;
+        }
+        return new \DateTimeImmutable($comparisonNow);
+    }
+
     /** @deprecated */
     public static function DateToday()
     {
@@ -87,7 +100,7 @@ class TimeUtil
 
     public static function now(bool $withFraction = false): string
     {
-        $obj = new \DateTime();
+        $obj = static::comparisonNow() ?? new \DateTimeImmutable();
         return static::format($obj, $withFraction);
     }
 
@@ -182,11 +195,19 @@ class TimeUtil
     }
 
     public static function nowDateTime(): \DateTime{
+        $comparisonNow = static::comparisonNow();
+        if ($comparisonNow !== null) {
+            return \DateTime::createFromImmutable($comparisonNow);
+        }
         $now = time();
         return static::secondsToDateTime($now, false, true);
     }
 
     public static function nowDateTimeImmutable(): \DateTimeImmutable{
+        $comparisonNow = static::comparisonNow();
+        if ($comparisonNow !== null) {
+            return $comparisonNow;
+        }
         $now = time();
         return static::secondsToDateTime($now, true, true);
     }