芹菜：在特定时间间隔后执行任务

I want to send an email to my users exactly 48 hours after they have registered.How do i achieve this using celery? If I create a periodic task to send an email, I will have to decide a specific time during which i want to execute that task. I don't want to keep run a celery task every second to check if there are any emails needed to be sent.I want to send an email to my users exactly 48