Reformed Gregorian calendars

Calendars in this category generally keep the features of the Gregorian calendar, such as

• a 400-year leap cycle of 146097 days = 20871 weeks and so a mean year of 365.2425 days.
• 12 months named January, February, March, April, May, June, July, August, September, October, November and December with more or less irregular lengths,
• 7-day week

They may change some of these to achieve particular benefits, but overall they are designed for calendar evolution, not revolution, which could be implemented gradually.