28/293 Calendar

If Javascript is enabled on your browser, what you should see is a calendar of the current month displayed using the 28/293 calendar. I call it the 28/293 calendar, because the calculation for where to place a leap day is based upon an accumulator.

The zero date has been set to the end date of the Mayan long count, which corresponds to the winter solstice that occurs when the sun travels through the intersection of the ecliptic and the Milky Way. In the Gregorian calendar, this date is December 21, 2012.

Years prior to this year are negative. If you have trouble thinking of negative years, think of B.C. (except that there is a year zero). Negative years here are analogous to years B.C. But in this case, we are living B.C. until the year 2012 (Gregorian).

Each month has an associated accumulator. This accumulator is incremented by 28 each month. If the number equals or exceeds 293 in a given month, an extra day is added to the month. Also, the accumulator is decremented by 293. In this way, a leap day is added every 10 or 11 months.

This month's accumulator is so next month's accumulator is (.

The color of each table cell is determined by the Gregorian date. So the color gradually changes with each day (green component) and has a jump each month (red component). There is another jump at the end of the Gregorian year (blue component). The color cycle repeats after 100 years. In order to maintain readability, only light colors are used. The red cell is today's date. The green cells are special days. A special day happens once every 294th day. The accumulator of the current month specifies the number of days between the last special day and the end of the current month.

New moon's have been calculated using simple arithmetic. If a new moon occurs in a month, it will be noted on the appropriate day in universal time. Click on the text to see how the calculations were made.

There are numerous advantages to this calendar. For now, I will leave it to you to search for other websites on 13 month 28 day calendars to see the advantages of that scheme. All the advantages of such calendars also apply to this one. The leap day scheme is where this calendar is unique. The main advantage is accuracy. This calendar is more consistent and accurate than the gregorian calendar. I've created a chart showing the error over time in the two calendars. Graphed are the summer solstice (blue:gregorian -- red:28/293) and the winter solstice (green:gregorian -- purple:28/293).

Below are last month's and next month's calendars.

Would you like to see what the calendar looks like on a given date? Use the left form to enter a date, and the 28/293 month containing that date will be rendered for you in a separate window. Use the right form to enter a date, and thirteen months starting with the date you entered will be rendered for you in a separate window. Note that currently this will work only for dates up to 12/21/2012.