diff --git a/src/Admin/AdminModule.php b/src/Admin/AdminModule.php
index e5f7f0f2..b1c13e11 100644
--- a/src/Admin/AdminModule.php
+++ b/src/Admin/AdminModule.php
@@ -533,28 +533,32 @@ public function maybe_test_payment() {
 			$subscription->set_description( $description );
 			$subscription->set_lines( $payment->get_lines() );
 
+			// Phase.
+			$phase = new SubscriptionPhase(
+				$subscription,
+				new DateTimeImmutable(),
+				new SubscriptionInterval( 'P' . $interval . Util::to_period( $interval_period ) ),
+				$price
+			);
+
 			// Ends on.
 			$total_periods = null;
 
 			if ( \array_key_exists( 'pronamic_pay_ends_on', $_POST ) ) {
+				$total_periods = null;
+
 				switch ( $_POST['pronamic_pay_ends_on'] ) {
 					case 'count':
-						$count = \filter_input( \INPUT_POST, 'pronamic_pay_ends_on_count', \FILTER_VALIDATE_INT );
-
-						if ( ! empty( $count ) ) {
-							$total_periods = $count;
-						}
+						$total_periods = (int) \filter_input( \INPUT_POST, 'pronamic_pay_ends_on_count', \FILTER_VALIDATE_INT );
 
 						break;
 					case 'date':
 						$end_date = \array_key_exists( 'pronamic_pay_ends_on_date', $_POST ) ? \sanitize_text_field( \wp_unslash( $_POST['pronamic_pay_ends_on_date'] ) ) : '';
 
 						if ( ! empty( $end_date ) ) {
-							$interval_spec = 'P' . $interval . Util::to_period( $interval_period );
-
 							$period = new \DatePeriod(
-								new \DateTime(),
-								new \DateInterval( $interval_spec ),
+								$phase->get_start_date(),
+								$phase->get_interval(),
 								new \DateTime( $end_date )
 							);
 
@@ -563,17 +567,13 @@ public function maybe_test_payment() {
 
 						break;
 				}
-			}
 
-			// Phase.
-			$phase = new SubscriptionPhase(
-				$subscription,
-				new DateTimeImmutable(),
-				new SubscriptionInterval( 'P' . $interval . Util::to_period( $interval_period ) ),
-				$price
-			);
+				if ( null !== $total_periods ) {
+					$end_date = $phase->get_start_date()->add( $phase->get_interval()->multiply( $total_periods ) );
 
-			$phase->set_total_periods( $total_periods );
+					$phase->set_end_date( $end_date );
+				}
+			}
 
 			$subscription->add_phase( $phase );
 
diff --git a/src/Subscriptions/SubscriptionPhase.php b/src/Subscriptions/SubscriptionPhase.php
index f963fbbe..b66eed7b 100644
--- a/src/Subscriptions/SubscriptionPhase.php
+++ b/src/Subscriptions/SubscriptionPhase.php
@@ -474,6 +474,7 @@ private function add_interval( $date, $times = 1 ) {
 	 *
 	 * @param DateTimeImmutable $start_date Start date.
 	 * @return SubscriptionPeriod|null
+	 * @throws \Exception Throws exception on invalid date period.
 	 */
 	public function get_period( DateTimeImmutable $start_date = null ) {
 		if ( null === $start_date ) {
@@ -487,7 +488,11 @@ public function get_period( DateTimeImmutable $start_date = null ) {
 		$end_date = $this->add_interval( $start_date );
 
 		if ( null !== $this->end_date && $end_date > $this->end_date ) {
-			return null;
+			$end_date = $this->end_date;
+
+			if ( $start_date > $end_date ) {
+				throw new \Exception( 'The start date of a subscription period cannot be later than the end date.' );
+			}
 		}
 
 		$period = new SubscriptionPeriod( $this, $start_date, $end_date, $this->get_amount() );
@@ -675,24 +680,19 @@ public static function align( self $phase, \DateTimeInterface $align_date ) {
 
 		$alignment_phase = new self( $phase->get_subscription(), $start_date, $alignment_interval, $phase->get_amount() );
 
-		$alignment_phase->set_total_periods( 1 );
-		$alignment_phase->set_alignment_rate( $alignment_difference->days / $regular_difference->days );
+		$alignment_end_date = $start_date->add( $alignment_interval );
 
-		// Remove one period from regular phase.
-		$total_periods = $phase->get_total_periods();
+		$alignment_phase->set_end_date( $alignment_end_date );
+		$alignment_phase->set_alignment_rate( $alignment_difference->days / $regular_difference->days );
 
-		if ( null !== $total_periods ) {
-			$phase->set_total_periods( $total_periods - 1 );
-		}
+		$phase->set_start_date( $alignment_end_date );
 
-		$alignment_end_date = $alignment_phase->get_end_date();
+		if ( null !== $phase->end_date ) {
+			$end_date = $phase->end_date->add( $alignment_interval );
 
-		if ( null === $alignment_end_date ) {
-			throw new \Exception( 'The align phase should always end because this phase exists for one period.' );
+			$phase->set_end_date( $end_date );
 		}
 
-		$phase->set_start_date( $alignment_end_date );
-
 		return $alignment_phase;
 	}
 }