A couple of years ago I had the loopy idea of creating a Space Age (Earth) calendar, different from the present Julian-Gregorian one, which would commemorate various feats of space exploration. I got as far as working out the arithmetical details, but never applied the finishing touches of the names for the days and months.

The calendar was to begin on October 4 of any (recent) Gregorian year, both as the first day of the year itself and the first day of its own (Space Age) era, commemorating the launch of Sputnik 1. Thus Year One went from October 4, 1957 to October 3, 1958; the current year is Year 49, and ends on October 3, 2006.
The year was 365 days long, 366 in leap years, which I set as Year Three and every fourth year after that, so that a Gregorian leap day would always fall in a Space Age leap year. The leap day in the Space Age calendar was, however, to be the last day of the year (so a numerical enumeration of days in the year would never be thrown off). Over longer time periods, the calendar would be adjusted by omitting the leap day every 128 years.
I didn't have any clear ideas about weekdays; one thought was to name them after planets (the original inspiration for our weekday names, but in ancient cosmology). There are more planet-names than days in a week, but I suppose in a Space-Age calendar the week wouldn't have to be seven days long. An even bigger problem is that right now we don't know how many planets there are going to be at the end of the year (except that it probably won't be nine)!
Each month was to consist of 30 days, with 5 "extra" days at the end of the year (6 in leap years). The last 5 days were to have their own names, which I thought might be of notable scientists who were instrumental in the dawning of the Space Age: perhaps Tsiolkovsky, Oberth, Goddard and I don't know who else -- von Braun and Korolev come to mind, but those choices might be more questionable than the first three.
The months in a non-leap year would correspond to the following days of the Gregorian calendar:
1 - October 4 - November 2
2 - November 3- December 2
3 - December 3 - January 1
4 - January 2 - January 31
5 - February 1 - March 2
6 - March 3 - April 1
7 - April 2- May 1
8 - May 2 - May 31
9 - June 1 - June 30
10 - July 1 - July 30
11 - July 31 - August 29
12 - August 30 - September 28
Last 5 days: September 29 - October 3

My naming concept for the months was that each month was to be named for a program which had had a significant event occur in it. So Month 1 would, of course, be Sputnik, and Month 10 (containing July 20, the day of the lunar landing) would be Apollo. But this is where I need some help: what, so far, are the twelve most important events of the Space Age? I'd like to include events from both manned and unmanned spaceflight.

Interesting idea, David.
Probably I'm mad, but I always found unaccaptable to have variable lenght months... I would prefere to have 13 months of 28 days plus 1(2) "extra-month" day each year.
Note that 28 days is closer to sidereal month and is a multiple of 7, so if we call the extra day(s) in another way, this allow to have each month of each year starting with a Monday and so on... in other words, this would make unnecessary to use the calendar!
Probably the idea isn't new and many will find unacceptable to have a prime number of months in a year, making difficult to use seasons or quarters. I think drawbacks are unavoidable due to "odd" astronomical time ratios but this is my preferred solution...

It would be easy enough to divide the year into quarters, each lasting 3 28-day months and one 7-day week = 91 days (with the final quarter having one or two extra days) -- hardly any more difficult than the current system, which is actually more uneven (1st quarter = 90 or 91 days, 2nd quarter = 91 days, third quarter = 92 days, 4th quarter = 92 days)

If it were up to me, I would scrap the current months and have the main subdivisions of the year be the 91-day quarters, divided into 13 7-day weeks, plus one extra day each year at the end of the fourth quarter, and the occasional leap day attached to the end of the second quarter.

Another possibility would be for five 73-day divisions, which would add up to 365 days, but 73 is a prime number, which is a big negative.

Bill