This is the actual text of the law[1]:
> The data subject shall have the right to obtain from the controller the erasure of personal data concerning him or her without undue delay
There is a one month limit of the right of access[2] and right to be informed[3], which flow into some of the articles of the law; and certain articles also mention a month's limit on being informed, e.g. from article 12 parts 3 and 4 [4]:
> The controller shall provide information on action taken on a request under Articles 15 to 22 to the data subject *without undue delay and in any event within one month* of receipt of the request. That period may be extended by two further months where necessary, taking into account the complexity and number of the requests. The controller shall inform the data subject of any such extension within one month of receipt of the request, together with the reasons for the delay. Where the data subject makes the request by electronic form means, the information shall be provided by electronic means where possible, unless otherwise requested by the data subject. If the controller does not take action on the request of the data subject, the controller shall inform the data subject without delay and at the latest within one month of receipt of the request of the reasons for not taking action and on the possibility of lodging a complaint with a supervisory authority and seeking a judicial remedy.
I've marked out those phrases because they show the language of the law that you will see again and again in the articles - without undue delay and within one month. The latter does not obviate the former.
Hence, and in fact, there is no part of the law that explicitly gives you a month to delete something. If you could delete something right now but you leave it hanging around because you have arbitrarily chosen a job to run once a month and there's a leak in that time, that would be undue delay.
[1] https://gdpr-info.eu/art-17-gdpr/
[2] https://gdpr-info.eu/issues/right-of-access/