What is Chronos?

Currently, there are versions available for VisualWorks, Squeak and Dolphin--although the Squeak and Dolphin versions lack some of the functionality herein described.

Chronos has been designed and architected for inter-Smalltalk portability. It is intended as a reference/standard implementation of advanced, rich date/time functionality for all Smalltalk flavors.

The current distribution is a beta version--mostly because there will probably be significant API changes in order to more fully support leap seconds.

Chronos Functionality Summary

• Supports business, legal, historical and scientific use cases:
  
  
  • Provides time-of-day-preserving date arithmetic, so that adding days or months doesn't change the time-of-day when crossing a DST transition.
  
  
  • Provides full support for both scientific (scale-invariant) and civil (calendar/business/legal) durations.
  
  
  • Supports point-in-time values that are either invariant to Universal Time (as required by the ANSI Standard) or invariant to nominal time. UT-invariant point-in-time values compare as equal to all others whose designation in Universal Time is the same--regardless of their time zone or designation in local time. Nominal-time-invariant point-in-time values compare as equal to all others with the same local ("nominal") time, regardless of time zone or designation in Universal Time--so a single instance can correctly specify the first moment of New Year's Day (of a particular year) in any time zone. (Example of a problem solvable by means of nominal-time invariance.)
  
  
  • Provides for the definition/detection of annually-recurring events (e.g., holidays, anniversaries, legal deadlines, number of trading days on the NYSE between two dates...)
  
  
  • Provides resolution down to the nanosecond.


• Provides comprehensive time zone functionality:
  
  
  • Fully supports the world-wide time zone rulesets defined by the Olson Timezone Database (the native time zone database of UNIX/MacOS X.)
  
  
  • Supports diachronic time zone rules that can change from one year to the next (For example, although you might know that Hawaii's current time zone offset is -10 hours, what you might not know is that on Dec 7, 1941 Hawaii's time zone offset was -10:30 hours. Chronos, however, knows this.)
  
  
  • Can automatically discover the local time zone from the Windows Registry or from the TZ "Environment Variable" (UNIX/MacOS X or Windows.)
  
  
  • Enables updating time zone rules without changing your application code (NOTE: US Daylight Saving Time extended by 4 weeks)


• Supports various calendrical systems in addition to the international standard Gregorian calendar (e.g., Julian, Hebrew, Islamic, Persian...).


• Provides very flexible formatting of date/time values, including extensible support for multiple locales, and "built in" support for ISO 8601 and RFC 2822 formats.


• Provides very flexible parsing of dates, times and date-and-time values from character data--including full support for ISO 8601, RFC 2822, time zone names, time zone abbreviations and time zone offsets.


• Provides high performance--usually significantly faster than the competition.

Getting Started Using Chronos

External Documentation

Documentation in the code itself

Most of the documentation for Chronos is in the code itself. The following "core API" classes have comments that should prove especially helpful in learning to use and obtain value from Chronos:

Although they are "core API" classes, the following have not yet been fully commented (although the ANSI Smalltalk Standard serves as an excellent reference for some of them):