Based on the search results, it is not possible to determine which Muslim holiday is tomorrow. The dates of Islamic holidays are based on the phases of the moon, and the dates of some festivals may depend on the actual sighting of the moon. This means that the same holiday may be observed on different days in different countries. However, it is worth noting that there are two official holidays in Islam, Eid al-Fitr and Eid al-Adha, which are celebrated by Muslims worldwide.