There are many synonyms for the phrase "during the day." Some of them include "daytime," "while the sun is up," "in daylight hours," "when it's light out," "throughout the day," "during daylight," "in the daytime," and "while it's bright out." These synonyms are useful when describing events or activities that occur specifically during the day, and can be used in a variety of situations, from discussing work schedules to planning outdoor activities. Choosing the right synonym can add variety and interest to your writing and can help you effectively convey your message.