Ключевые слова: 15, 15 december, agenda, appointment, birthday, block, business, calendar, celebrate, celebration, concept, conceptual, cube, date, day, deadline, december, december calendar, education, elearning, event, fifteenth day december, freelance, holiday, international, job, labor, lifestyle, month, monthly, notice, number, office, organizer, plan, planner, planning, reminder, schedule, season, start, symbol, time, week, white, winter, wooden, work, workplace,