Add periodisless definition for periods of same type. This allows for consistent ordering for multiple periods in a CompoundPeriod. Not sure if it's really helpful, but maybe.
Add functionality for customizing locale for dayname, daynameabbr, monthname, and monthnameabbr. A user can now define their own dict mapping days of the week or months of the year integers to custom locale names and see the results by using the locale keyword in those functions.