Ключевые слова: 13, agenda, appointment, april, background, begin, birth, birthday, black, calendar, concept, conceptual, cube, daily, date, day, day 13, deadline, diary, event, festive, happy, holiday, important, meeting, month, monthly, note, number, object, office, organizer, party, pen, plan, planner, remember, remind, reminder, schedule, space, spring, time, week, white, wood, year,