Date Functions: Basic Date Functions

Description

Some more date functions for making daily life a bit easier. The first ones extract a specific part of a given date, others check some conditions.

Usage

Year(x)
Quarter(x)
Month(x, fmt = c("m", "mm", "mmm"), lang = c("local", "engl"), 
      stringsAsFactors = TRUE)
Week(x, method = c("iso", "us"))
Day(x)
Weekday(x, fmt = c("d", "dd", "ddd"), lang = c("local", "engl"), 
        stringsAsFactors = TRUE)
YearDay(x)
YearMonth(x)

Day(x) <- value

IsWeekend(x)
IsLeapYear(x)

Hour(x)
Minute(x)
Second(x)

Now()
Today()

DiffDays360(start_d, end_d, method = c("eu", "us"))
LastDayOfMonth(x)

Arguments

the date to be evaluated.

fmt

format string, defines how the month or the weekday are to be formatted. Defaults to "m", resp. "d". Is ignored for other functions.

value

new value

lang

the language for the months and daynames. This can be either the current locale (default) or english.

stringsAsFactors

logical. Defines if the result should be coerced to a factor, using the local definitions as levels. The result would be an ordered factor. Default is TRUE.

start_d, end_d

the start, resp. end date for DiffDays360.

method

one out of "eu", "us", setting either European or US-Method calculation mode. Default is "eu".

Value

a vector of the same dimension as x, consisting of either numeric values or characters depending on the function used.

Details

These functions are mainly convenience wrappers for the painful format() and its strange codes... Based on the requested time component, the output is as follows: Year returns the year of the input date in yyyy format. Quarter returns the quarter of the year (1 to 4) for the input date. Month returns the month of the year (1 to 12) for the input date. Week returns the week of the year for the input date (0 to 53), as defined in ISO8601. Weekday returns the week day of the input date. (1 - Monday, 2 - Tuesday, ... 7 - Sunday). (Names and abbreviations are either english or in the current locale!) YearDay returns the day of the year numbering (1 to 366). Day returns the day of the month (1 to 31). YearMonth returns the yearmonth representation (yyyymm) of a date as long integer. Hour, Minute Second return the hour, minute resp. second from a Posixlt object. Today, Now return the current date, resp. the current date and time. IsWeekend returns TRUE, if the date x falls on a weekend. IsLeapYear returns TRUE, if the year of the date x is a leap year. The day can not only be extracted, but as well be defined. See examples. DiffDays360 calculates the difference between 2 dates using the 360-days convention. LastDayOfMonth returns the last day of the month of the given date(s).

Examples

Run this code

x <- Today()    # the same as Sys.Date() but maybe easier to remember..  

Year(x)
Quarter(x)

Month(x)
Month(x, fmt = "mm", lang="engl")
Month(x, fmt = "mm", lang="local")
Month(x, fmt = "mmm", lang="engl")
Month(x, fmt = "mmm", lang="local")

Week(x)

Day(x)
Day(x) <- 20
x

Weekday(x)
Weekday(x, fmt = "dd", lang="engl")
Weekday(x, fmt = "dd", lang="local")
Weekday(x, fmt = "ddd", lang="engl")
Weekday(x, fmt = "ddd", lang="local")

YearDay(x)

IsWeekend(x)

IsLeapYear(x)

# let's generate a time sequence by weeks
Month(seq(from=as.Date(Sys.Date()), to=Sys.Date()+150, by="weeks"), fmt="mm")

LastDayOfMonth(as.Date(c("2014-10-12","2013-01-31","2011-12-05")))

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