Date Functions {DescTools}

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 = DescToolsOptions("lang"),
      stringsAsFactors = TRUE)
Week(x, method = c("iso", "us"))
Day(x)
Weekday(x, fmt = c("d", "dd", "ddd"), lang = DescToolsOptions("lang"),
        stringsAsFactors = TRUE)
YearDay(x)
YearMonth(x)

Day(x) <- value

IsWeekend(x)
IsLeapYear(x)

Hour(x)
Minute(x)
Second(x)
Timezone(x)
HmsToMinute(x)

Now()
Today()

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

Arguments

x

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

optional value setting the language for the months and daynames. Can be either "local" for current locale or "engl" for english. If left to NULL, the option "lang" will be searched for and if not found "local" will be taken as default.

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".

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 or a yearmonth yyyymm.
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 or for a yearmonth yyyymm.
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, Timezone return the hour, minute, second or timezone from a POSIXlt object.
HmsToMinute converts the time parts of a POSIXlt object to minutes.
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). YearDays returns the total number of days of the given date(s). MonthDays returns the numer of days of the month of the given date(s).

The language in Weekday and Moth can be set with an option as well. The functions will check for an existing option named "lang" and take this value if it exists. So simply set option(lang="engl") if the results should always be reported in English.

Value

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

Author(s)

Andri Signorell <[e-mail]>

See Also

strptime, DateTimeClasses, as.POSIXlt

Examples

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")))