Does the word "day" in the Hadith "None has the right to be worshipped but Allah alone, Who has no partner..." refer to the period from dawn until sunset, or until the end of the full day, and must the hundred be completed before sunset?

The hadith referred to in the question was narrated by Muslim, and its wording is that the Messenger of Allah, peace and blessings be upon him, said: "Whoever says: 'There is no god but Allah, alone, without partner. To Him belongs all sovereignty and all praise, and He is over all things competent,' a hundred times in a day, it will be for him the equivalent of freeing ten slaves, and a hundred good deeds will be written for him, and a hundred bad deeds will be erased from him, and it will be a protection for him from Satan on that day until evening. No one will come with anything better than what he came with, except for one who does more than that. And whoever says: 'Glorified is Allah and praised be He,' a hundred times in a day, his sins will be forgiven, even if they were like the foam of the sea."

It is best for this dhikr to be recited consecutively at the beginning of the day to serve as a protection throughout the entire day, but there is no harm in reciting it separately. What is apparent is that "day" here refers to the daylight hours (between dawn and sunset).

Some narrations mention that the hundred repetitions are to be said in the morning and evening, as in the narration by An-Nasa'i from Amr ibn Shu'ayb, from his father, from his grandfather: "Whoever says two hundred times in a day: 'There is no god but Allah, alone, without partner. To Him belongs all sovereignty and all praise, and He is over all things competent,' no one before him will have surpassed him, and no one after him will catch up to him, except for one who does better than him." This means a hundred in the morning and a hundred in the evening.