Based on the search results, there are several celebrations happening tomorrow. Here are some of them:

• One Health Day: This is a day to promote the idea that the health of humans, animals, and the environment are interconnected.
• World Vegan Day: This day celebrates the benefits of a vegan lifestyle and encourages people to try veganism.
• National Sandwich Day: This day pays homage to the culinary invention of sandwiches, recognizing their historical significance.
• World Cancer Research Day: This day raises global awareness for cancer researchs vital role in saving lives.

Its important to note that the celebrations listed above are not exhaustive, and there may be other celebrations happening tomorrow that are not mentioned in the search results.