The word "daytimer" is often used to describe a person who is busy and productive during the day. However, there are several alternatives to this term that can be used interchangeably. For instance, the word "day planner" is a great synonym for "daytimer" and has the added connotation of someone who plans their day meticulously. Another synonym for "daytimer" is "day scheduler" which describes someone who schedules their time very effectively. "Day organizer" is another similar synonym, which implies the person is able to organize their day with ease. Lastly, "daytime planner" is another term that can be used to describe someone who is productive during the day.