清明 (qing ming) is tomb sweeping day, the next holiday is on labour day which is may 1st( 5th month 1st day) hence, 五一.
The ghost wants you to clean their tombs, and absolutely won't let you leave until may 1st? But if we translated 清明 seperately perhaps it could be this: The ghost wants to let you to died quietly/naturally and absolutely won't let you pass the 1st May.
The ghost wants you dead by Tomb Sweeping Day, and would absolutely not let you live past 1st of May.
清明/the tomb sweeping holiday is in April. That phrase basically is saying that if a ghost wants to kill you on the tomb sweeping day, you won't live till the first of the next month (may).