The code in this library section is not supported by StatSci.

This section contains an implementation of chron objects.
These objects handle dates and times. For the time being issues relating to 
time-zones, daylight savings time, etc. are being put aside.
The material was developed at AT&T Bell Labs and is experimental.

The following methods and functions are available for chron objects:

function	description
----------	-----------------------------------------------------
chron		creates a chron object; it takes either julian dates
		or character dates. See help(chron).
dates		creates a dates object (simply invokes chron)
times		creates a times object (simply inovkes chron)

as.numeric	returns a vector of julian dates + fraction of day (times)
as.character	returns a character representation of dates/times
is.na

print		print dates and times nicely 
plot		plot with time axis
hist		histogram with time axis
identify	identify points in scatterplot
lines, points	add lines/points
axis.times	add time axis to plot
cut		make ordered factors from dates (e.g., by month, week)
seq		generate a sequence of dates

min, max, 	numeric summaries
range, summary		
sort, order
trunc, ceiling,
round, signif,
diff

[.times		selects, e.g., dates[ dates > "02/20/92" ], or
		lathe.date[ start.date > min(scan.date) ]

[<-.times	replacement
c		combines chrons

days, months, 	extract day, month, year, quarter number, etc.
years, quarters		
weekdays,
hours, minutes, 
seconds

is.holiday
is.weekend

month.day.year 	date conversion (modified from the S "blue" book) 
julian,
day.of.week

UNDOCUMENTED FEATURES:
----------------------
	1. Chron matrices can be created from chron objects by using dim() 
	   (can't use matrix() nor array())
	   > dim(x) <- c(20,3)
	   > x[2,3] <- "03/28/90"	 # replaces a cell

	2. The c() method takes anything that can be coerced to chrons:
	   y <- c(x, "03/21/92", 8123)
	   but a bug(?) in the S evaluator makes it necessary to 
	   specify the chron object first, i.e., c("03/28/90", x) does not
	   dispath the c.dates() method.

For more information on chron objects see:
David A. James and Daryl Pregibon, "Chronological Objects in S",
AT&T Bell Laboratories Tech. Report (Oct. 1992).