<input class="form-control" id="dueDate" type="datetime-local" th:field="*{dueDate}"/>

public class TaskDTO {
     private long id;
     @Size(min=8)
     @NotNull
     private String name;
     @Size(min=8)
     @NotNull
     private String description;
     @NotNull
     private String priority;
     @Size(min=8)
     @NotNull
     private String location;
     private boolean completed;
     @DateTimeFormat(pattern = "dd-MM-yyyy HH:mm")
     @NotNull
     private LocalDateTime dueDate;


     //getters e setters omitidos
}

@PostMapping("/dashboard/task/{id}")
public String TaskForm(@Valid @ModelAttribute("taskDTO")TaskDTO taskDTO,BindingResult bidingResult,@PathVariable("id")long id) {
    if(bidingResult.hasFieldErrors()) {
        //
    }
    Project p = projectRepository.findById(id).get();
    Task t = taskDTO.generateTask(p);
    taskRepository.save(t);
    return "main";
}