A new calendar based on 365 days in a year and 366 days in leap years. The calendar is characterized in having 13 months in a year, 12 of which include 28 days organised into 4 weeks each consisting of 7 days, and one of which includes 29 days organized into 4 weeks each consisting of 7 days, plus an extra day. The calendar is further organized in a manner that every date in a month falls on the same day of the week as the same date in any other months of the year. The thirteen months of the new calendar year in chronological order are the 'zero month', 'first month', 'second month', 'third month', 'fourth month', 'fifth month', 'sixth month', 'seventh month', 'eighth month', 'ninth month', 'tenth month', 'eleventh month', and ' twelfth month'. The first day of the zero month is numerically numbered as day 0, and the remaining days are numerically numbered as day 1 through day 28 day. The first day of each of the other 12 months is numerically numbered as day one (1), and the remaining 27 days are numerically numbered as days 2 through 28. In one embodiment, day 1 of each month falls on a Sunday to coincide with the way the days of the week appear in the current calendar. In another embodiment, day 1 of each month falls on a Saturday to coincide with the way the days of the week are numbered in the current calendar.