Current Idea: A year is either 365 or 366 days. Leap years occur for years mod 4 = 0, unless that year mod 64 = 0, in which case it is not a leap year, unless that year mod 128 = 0, in which case it is. (Every fourth year is a leap year. Every sixty-fourth is not. Every hundred-and-twenty-eighth is. Later rules trump earlier rules.) This gives an average year length of 365.2421875 days. In comparison, the tropical year for 1994-1998 is 365.242190 days. (Using the traditional 4,100,400 leap year scheme, the average length is 365.2425 days ) The year starts at what in the old system is Dec 23. This is, on average, the first day where the day is longer than the night. Due to leap year inaccuracies, Dec 24 may be this day at times. Yet, we do not adjust the year to fix this. All years start on the same day, removing the requirement for a complicated Doomsday-style algorithm to calculate weekdays. Weeks: 36 10 day weeks, three of whose days are non-working for most (similar to Saturday and Sunday of the current calendar), plus one final mop-up week of 5 or 6 days, depending on leap. Due to the all years start on the same day, this means that the mop up week will deprive us of days 7,8,9,10 and possibly 6. This is favorable to the alternative, wherein the week "wraps around" (as in the current calendar), IMHO. Hence, set the three "free-from-ordinary-work" days to be at the start of the week. Months: Here we have two options. Either fix months so that a full moon appears at the same time each month (subject to leap months), or simply use them as a larger time unit than a week. In the first case, each month would be 30 days, except for every other, except for every twenty-second except for every sixty-sixth. This seems too complicated, and would also have to take the mop-up week into account, although it would be nice to get one more free day every other month (roughly) due to the first term of the lunar cycle approximation. Thus we divide each month into 3 weeks = 30 days. This results in 12 months. The last month will be unusual in that it contains 35 or 36 days depending on leap, instead of just 30. Years: We'd like to set the year so that some power of ten is the start of the universe, and so that years around now have no more than four digits. However, this requires knowledge of the Hubble constant, and the uncertainity in this constant is currently too great. In any case, year 0 is a year. This gets rid of all the "2001 is the real millennium" "math geek" stuff. ============================================================================== Hours, Minutes, Seconds: First, we have to call these units something else as not to confuse them with ordinary hours / minutes / seconds. Using simplicity, say Hours', Minutes', and Seconds' (prime units). Then: There are 20 Hours' in a day 100 Minutes' in a Hour' and 10 Seconds' in a Minute'. This resolves to: Each hour' is 1.2 hours, or 72 minutes. Each minute' is 1/100 of that, or 72/100 = 0.72 minutes. This is equivalent to 60*0.72 = 43.2 seconds. Each second' is 1/100 of a minute', or 43.2/10 seconds. This is equivalent to 4.32 seconds. -