Ключевые слова: 13, 13th, agenda, anniversary, annual, appointment, background, blank, business, calendar, calender, concept, countdown, daily, date, day, deadline, design, diary, event, holiday, important, mark, marker, meeting, memo, month, monthly, note, number, object, office, organize, organizer, page, plan, planner, remember, reminder, schedule, season, sign, symbol, thirteen, thirteenth, time, today, week, white, year,