diff --git a/.baseline-phan.php b/.baseline-phan.php
index 540fa4b..92adce6 100644
--- a/.baseline-phan.php
+++ b/.baseline-phan.php
@@ -34,7 +34,6 @@
     // PhanPossiblyNullTypeMismatchProperty : 1 occurrence
     // PhanReadOnlyPrivateProperty : 1 occurrence
     // PhanTypeInvalidLeftOperandOfNumericOp : 1 occurrence
-    // PhanTypeMismatchArgumentInternal : 1 occurrence
     // PhanTypeMismatchPropertyReal : 1 occurrence
     // PhanTypeMismatchReturnNullable : 1 occurrence
     // PhanUnextractableAnnotationElementName : 1 occurrence
@@ -74,7 +73,7 @@
         'src/Model/Feature/Subscribed/SubscribedCountableFeature.php' => ['ConstReferenceClassNotImported', 'PhanUndeclaredMethod'],
         'src/Model/Feature/Subscribed/SubscribedFeaturesCollection.php' => ['PhanTypeMismatchArgument', 'PhanTypeMismatchDeclaredReturn', 'PhanUnreferencedProtectedMethod'],
         'src/Model/Feature/Subscribed/SubscribedRechargeableFeature.php' => ['PhanCompatibleUnionType', 'PhanTypeMismatchReturnSuperType'],
-        'src/Model/Invoice.php' => ['PhanDeprecatedFunction', 'PhanParamSignatureMismatch', 'PhanTypeArraySuspicious', 'PhanTypeMismatchArgumentInternal', 'PhanTypeMismatchArgumentNullable', 'PhanTypeMismatchDimAssignment', 'PhanTypeMismatchReturn', 'PhanTypeMismatchReturnNullable'],
+        'src/Model/Invoice.php' => ['PhanDeprecatedFunction', 'PhanParamSignatureMismatch', 'PhanTypeArraySuspicious', 'PhanTypeMismatchArgumentNullable', 'PhanTypeMismatchDimAssignment', 'PhanTypeMismatchReturn', 'PhanTypeMismatchReturnNullable'],
         'src/Model/InvoiceInterface.php' => ['PhanUnextractableAnnotationElementName', 'PhanUnextractableAnnotationSuffix'],
         'src/Model/InvoiceLine.php' => ['PhanPossiblyNullTypeMismatchProperty'],
         'src/Model/InvoiceSection.php' => ['PhanDeprecatedFunction', 'PhanTypeMismatchArgumentNullable', 'PhanTypeMismatchDimAssignment', 'PhanTypeMismatchPropertyReal'],
diff --git a/.baseline-phpstan.neon b/.baseline-phpstan.neon
index 2864d9a..64a11f4 100644
--- a/.baseline-phpstan.neon
+++ b/.baseline-phpstan.neon
@@ -590,6 +590,11 @@ parameters:
 			count: 1
 			path: src/Model/Invoice.php
 
+		-
+			message: "#^Class DateTime is unsafe to use\\. Its methods can return FALSE instead of throwing an exception\\. Please add 'use Safe\\\\DateTime;' at the beginning of the file to use the variant provided by the 'thecodingmachine/safe' library\\.$#"
+			count: 1
+			path: src/Model/Invoice.php
+
 		-
 			message: "#^Method SerendipityHQ\\\\Bundle\\\\FeaturesBundle\\\\Model\\\\Invoice\\:\\:getLine\\(\\) has parameter \\$id with no type specified\\.$#"
 			count: 1
@@ -625,16 +630,6 @@ parameters:
 			count: 1
 			path: src/Model/Invoice.php
 
-		-
-			message: "#^Parameter \\#2 \\$datetime of static method DateTime\\:\\:createFromFormat\\(\\) expects string, float given\\.$#"
-			count: 1
-			path: src/Model/Invoice.php
-
-		-
-			message: "#^Property SerendipityHQ\\\\Bundle\\\\FeaturesBundle\\\\Model\\\\Invoice\\:\\:\\$issuedOn \\(DateTimeInterface\\) does not accept DateTime\\|false\\.$#"
-			count: 1
-			path: src/Model/Invoice.php
-
 		-
 			message: "#^Result of && is always false\\.$#"
 			count: 1
@@ -650,16 +645,6 @@ parameters:
 			count: 1
 			path: src/Model/Invoice.php
 
-		-
-			message: "#^Strict comparison using \\=\\=\\= between null and DateTimeInterface will always evaluate to false\\.$#"
-			count: 1
-			path: src/Model/Invoice.php
-
-		-
-			message: "#^Strict comparison using \\=\\=\\= between null and SerendipityHQ\\\\Component\\\\ValueObjects\\\\Money\\\\MoneyInterface will always evaluate to false\\.$#"
-			count: 2
-			path: src/Model/Invoice.php
-
 		-
 			message: "#^Method SerendipityHQ\\\\Bundle\\\\FeaturesBundle\\\\Model\\\\InvoiceLine\\:\\:__toArray\\(\\) return type has no value type specified in iterable type array\\.$#"
 			count: 1
diff --git a/.baseline-psalm.xml b/.baseline-psalm.xml
index fee4344..991c589 100644
--- a/.baseline-psalm.xml
+++ b/.baseline-psalm.xml
@@ -406,6 +406,9 @@
     <InvalidNullableReturnType>
       <code><![CDATA[InvoiceLine]]></code>
     </InvalidNullableReturnType>
+    <InvalidOperand>
+      <code><![CDATA[\microtime(true)]]></code>
+    </InvalidOperand>
     <InvalidReturnStatement>
       <code><![CDATA[$return]]></code>
     </InvalidReturnStatement>
@@ -424,31 +427,21 @@
     <NullableReturnStatement>
       <code><![CDATA[$this->sections[self::SECTION_DEFAULT]->getLine($id)]]></code>
     </NullableReturnStatement>
-    <PropertyNotSetInConstructor>
-      <code><![CDATA[$grossTotal]]></code>
-      <code><![CDATA[$issuedOn]]></code>
-      <code><![CDATA[$netTotal]]></code>
-    </PropertyNotSetInConstructor>
     <RedundantCondition>
       <code><![CDATA['string']]></code>
     </RedundantCondition>
     <RedundantConditionGivenDocblockType>
       <code><![CDATA[\is_int($id)]]></code>
     </RedundantConditionGivenDocblockType>
-    <TypeDoesNotContainNull>
-      <code><![CDATA[null === $this->grossTotal]]></code>
-      <code><![CDATA[null === $this->issuedOn]]></code>
-      <code><![CDATA[null === $this->netTotal]]></code>
-    </TypeDoesNotContainNull>
+    <RedundantPropertyInitializationCheck>
+      <code><![CDATA[false === isset($this->grossTotal)]]></code>
+      <code><![CDATA[false === isset($this->issuedOn)]]></code>
+      <code><![CDATA[false === isset($this->netTotal)]]></code>
+    </RedundantPropertyInitializationCheck>
     <UndefinedMethod>
       <code><![CDATA[$section]]></code>
       <code><![CDATA[$section]]></code>
     </UndefinedMethod>
-    <UninitializedProperty>
-      <code><![CDATA[$this->grossTotal]]></code>
-      <code><![CDATA[$this->issuedOn]]></code>
-      <code><![CDATA[$this->netTotal]]></code>
-    </UninitializedProperty>
   </file>
   <file src="src/Model/InvoiceInterface.php">
     <InvalidDocblock>
diff --git a/src/Model/Invoice.php b/src/Model/Invoice.php
index b75c9b6..4455a5f 100644
--- a/src/Model/Invoice.php
+++ b/src/Model/Invoice.php
@@ -56,16 +56,16 @@ public function __construct($currency)
         $this->currency = $currency;
 
         // Set the issue date
-        if (null === $this->issuedOn) {
+        if (false === isset($this->issuedOn)) {
             // Create it with microseconds, so it is possible to use the createdOn to create a unique invoice number (http://stackoverflow.com/a/28937386/1399706)
-            $this->issuedOn = \DateTime::createFromFormat('U.u', \microtime(true));
+            $this->issuedOn = new \DateTime('@' . \microtime(true));
         }
 
-        if (null === $this->grossTotal) {
+        if (false === isset($this->grossTotal)) {
             $this->grossTotal = new Money([MoneyInterface::BASE_AMOUNT => 0, MoneyInterface::CURRENCY => $this->getCurrency()]);
         }
 
-        if (null === $this->netTotal) {
+        if (false === isset($this->netTotal)) {
             $this->netTotal = new Money([MoneyInterface::BASE_AMOUNT => 0, MoneyInterface::CURRENCY => $this->getCurrency()]);
         }