backend/src/main/java/core/api/controller/ScheduleController.java

@@ -140,4 +140,19 @@ public class ScheduleController {
             return ResponseEntity.status(404).body(new SimpleStatusResponse("failed"));
         }
     }
+
+    @PostMapping("schedules/{scheduleID}/activate")
+    public ResponseEntity<?> activateSchedule(@PathVariable long scheduleID) {
+        PermissionResult<AbstractSchedule> permissionResult = taskScheduleService.getSchedulePermissions(scheduleID, SecurityContextHolder.getContext().getAuthentication().getName());
+        if(permissionResult.isHasPermissions()) {
+            return ResponseEntity.status(403).body(new SimpleStatusResponse("failed"));
+        }
+
+        if(permissionResult.getExitCode() == ServiceExitCode.MISSING_ENTITY) {
+            return ResponseEntity.status(404).body(new SimpleStatusResponse("failed"));
+        }
+
+        ServiceResult<AbstractSchedule> serviceResult = taskScheduleService.activateSchedule(permissionResult.getResult());
+        return ResponseEntity.ok(new ScheduleActivateResponse(serviceResult.getResult().getStartTime()));
+    }
 }

backend/src/main/java/core/api/models/timemanager/taskSchedule/ScheduleActivateResponse.java

@@ -0,0 +1,22 @@
+package core.api.models.timemanager.taskSchedule;
+
+import java.time.LocalDateTime;
+
+public class ScheduleActivateResponse {
+    private LocalDateTime startTime;
+
+    public ScheduleActivateResponse(LocalDateTime startTime) {
+        this.startTime = startTime;
+    }
+
+    public ScheduleActivateResponse() {
+    }
+
+    public LocalDateTime getStartTime() {
+        return startTime;
+    }
+
+    public void setStartTime(LocalDateTime startTime) {
+        this.startTime = startTime;
+    }
+}

backend/src/main/java/core/services/TaskScheduleService.java

@@ -99,4 +99,12 @@ public class TaskScheduleService {
         Optional<AbstractSchedule> activeSchedule = scheduleRepository.getActiveScheduleOfUser(username);
         return activeSchedule.map(ServiceResult::new).orElseGet(() -> new ServiceResult<>(ServiceExitCode.MISSING_ENTITY));
     }
+
+    public ServiceResult<AbstractSchedule> activateSchedule(AbstractSchedule schedule) {
+        if(schedule.getStartTime() == null) {
+            schedule.setStartTime(LocalDateTime.now());
+            scheduleRepository.save(schedule);
+        }
+        return new ServiceResult<>(schedule);
+    }
 }

backend/src/test/java/core/schedules/ScheduleServiceTest.java

@@ -157,4 +157,25 @@ public class ScheduleServiceTest {
         assertEquals(ServiceExitCode.OK, result_3.getExitCode());
         assertThat(entityManager.find(BasicTaskSchedule.class, result_3.getResult().getScheduleID())).isNotNull();
     }
+
+    @Test
+    @SqlGroup({
+            @Sql("classpath:taskgroupRepositoryTestEntries.sql"),
+            @Sql("classpath:taskRepositoryEntries.sql"),
+            @Sql("classpath:basicScheduleEntries.sql")
+    })
+    void activateSchedule() {
+        //Activate already running schedule
+        ServiceResult<AbstractSchedule> result_1 = taskScheduleService.activateSchedule(entityManager.find(BasicTaskSchedule.class, 4L));
+        assertNotNull(result_1.getResult().getStartTime());
+        assertNull(result_1.getResult().getStopTime());
+
+        entityManager.remove(entityManager.find(BasicTaskSchedule.class, 4L));
+        assertThat(entityManager.find(BasicTaskSchedule.class, 4L)).isNull();
+
+        //Activate not running schedule
+        ServiceResult<AbstractSchedule> result_2 = taskScheduleService.activateSchedule(entityManager.find(BasicTaskSchedule.class, 5L));
+        assertNotNull(result_2.getResult().getStartTime());
+        assertNull(result_2.getResult().getStopTime());
+    }
 }