diff --git a/src/Model/TimeRange.php b/src/Model/TimeRange.php
index 3471b2a..0f17172 100644
--- a/src/Model/TimeRange.php
+++ b/src/Model/TimeRange.php
@@ -164,9 +164,26 @@ final readonly class TimeRange implements \Stringable
         return self::format($this->endMinute);
     }
 
+    /**
+     * One-sided spans read as "bis 13:00" / "ab 13:00" rather than 00:00–13:00 / 13:00–24:00:
+     * a half day booked by giving only one end has no meaningful other end, and midnight is not
+     * what the user typed.
+     */
     public function __toString(): string
     {
-        return $this->isAllDay() ? 'ganztägig' : $this->start().'–'.$this->end();
+        if ($this->isAllDay()) {
+            return 'ganztägig';
+        }
+
+        if (self::DAY_START === $this->startMinute) {
+            return 'bis '.$this->end();
+        }
+
+        if (self::DAY_END === $this->endMinute) {
+            return 'ab '.$this->start();
+        }
+
+        return $this->start().'–'.$this->end();
     }
 
     private static function minutesOf(\DateTimeInterface $time): int
diff --git a/tests/Controller/FloorPlanTest.php b/tests/Controller/FloorPlanTest.php
index 2663573..2504698 100644
--- a/tests/Controller/FloorPlanTest.php
+++ b/tests/Controller/FloorPlanTest.php
@@ -56,7 +56,7 @@ class FloorPlanTest extends WebTestCase
         $this->book($desk, $this->user('bea@ep-reisen.de', 'Bea Kranz'), 540, 780);
 
         self::assertSame(
-            ['Schreibtisch 01', 'Bea K. 09:00–13:00', 'frei 13:00–24:00'],
+            ['Schreibtisch 01', 'Bea K. 09:00–13:00', 'frei ab 13:00'],
             $this->linesOf($this->board()),
         );
     }
@@ -112,7 +112,7 @@ class FloorPlanTest extends WebTestCase
         $lines = $this->linesOf($this->board());
 
         self::assertSame(
-            ['Schreibtisch 01', 'Ann A. 00:00–06:00', 'Bea B. 06:00–12:00', '+2 weitere'],
+            ['Schreibtisch 01', 'Ann A. bis 06:00', 'Bea B. 06:00–12:00', '+2 weitere'],
             $lines,
         );
         // Label plus MAX_LINES, never more.
diff --git a/tests/Model/SpotTest.php b/tests/Model/SpotTest.php
index e58b224..1fa38ac 100644
--- a/tests/Model/SpotTest.php
+++ b/tests/Model/SpotTest.php
@@ -42,7 +42,7 @@ class SpotTest extends TestCase
         // Taken 09:00-13:00 leaves 00:00-09:00 (9h) and 13:00-24:00 (11h).
         $spot = $this->spot([$this->booking($this->someoneElse(), 540, 780)]);
 
-        self::assertSame('13:00–24:00', (string) $spot->suggested());
+        self::assertSame('ab 13:00', (string) $spot->suggested());
     }
 
     public function testTheSuggestedWindowIsAlwaysBookable(): void
diff --git a/tests/Model/TimeRangeTest.php b/tests/Model/TimeRangeTest.php
index 5952efd..603c1a0 100644
--- a/tests/Model/TimeRangeTest.php
+++ b/tests/Model/TimeRangeTest.php
@@ -149,6 +149,14 @@ class TimeRangeTest extends TestCase
         self::assertSame('yes', $twig->render('t', ['range' => TimeRange::wholeDay()]));
     }
 
+    public function testAOneSidedRangeReadsAsAbOrBis(): void
+    {
+        self::assertSame('bis 13:00', (string) TimeRange::fromMinutes(TimeRange::DAY_START, 13 * 60));
+        self::assertSame('ab 13:00', (string) TimeRange::fromMinutes(13 * 60, TimeRange::DAY_END));
+        self::assertSame('09:00–13:00', (string) TimeRange::fromMinutes(9 * 60, 13 * 60));
+        self::assertSame('ganztägig', (string) TimeRange::wholeDay());
+    }
+
     /**
      * @param list<TimeRange> $ranges
      *