Overall Design Goals

Category	Description	Functions
Interfaces	Provide concrete classes for manipulation of dates and times	date, time, date_duration, time_duration, date_period, time_period, etc support for infinity - positive infinity, negative infinity iterators over time and date ranges allow date and time implemenations to be separate as much as possible
Calculation	Provide a basis for performing efficient time calculations	days between dates durations of times durations of dates and times together
Representation Flexibility	Provide the maximum possible reusability and flexibility	traits based customization of internal representations for size versus resolution control Allowing the use of different epochs and resolution (eg: seconds versus microseconds, dates starting at the year 2000 versus dates starting in 1700) Options for configuring unique calendar representations (Gregorian + others) the use of Julian Day number and the conversion between this and the Gregorian/Julian calendar date Allow for flexible adjustments including leap seconds
Date Calculations	Provide tools for date calculations	provide basis for calculation of complex event specs like holidays calendar to calendar conversions provide for ability to extend to new calendar systems
Time Calculations	Provide concrete classes for manipulation of time	provide the ability to handle cross time-zone issues provide adjustments for daylight savings time (summer time)
Clock Interfaces	Provide classes for retrieving time current time	access to a network / high resolution time sources retrieving the current date time information to populate classes
I/O Interfaces	Provide input and output for time including	multi-lingual support provide ISO8601 compliant time facet use I/O facets for different local behavior