parse_date_time

User friendly date-time parsing functions

parse_date_time() parses an input vector into POSIXct date-time object. It differs from base::strptime() in two respects. First, it allows specification of the order in which the formats occur without the need to include separators and the % prefix. Such a formatting argument is referred to as "order". Second, it allows the user to specify several format-orders to handle heterogeneous date-time character representations.

parse_date_time2() is a fast C parser of numeric orders.

fast_strptime() is a fast C parser of numeric formats only that accepts explicit format arguments, just like base::strptime().

Usage

parse_date_time(
  x,
  orders,
  tz = "UTC",
  truncated = 0,
  quiet = FALSE,
  locale = Sys.getlocale("LC_TIME"),
  select_formats = .select_formats,
  exact = FALSE,
  train = TRUE,
  drop = FALSE
)
parse_date_time2(
  x,
  orders,
  tz = "UTC",
  exact = FALSE,
  lt = FALSE,
  cutoff_2000 = 68L
)
fast_strptime(x, format, tz = "UTC", lt = TRUE, cutoff_2000 = 68L)

Details

When several format-orders are specified, parse_date_time() selects (guesses) format-orders based on a training subset of the input strings. After guessing the formats are ordered according to the performance on the training set and applied recursively on the entire input vector. You can disable training with train = FALSE.

parse_date_time(), and all derived functions, such as ymd_hms(), ymd(), etc., will drop into fast_strptime() instead of base::strptime() whenever the guessed from the input data formats are all numeric.

The list below contains formats recognized by lubridate. For numeric formats leading 0s are optional. As compared to base::strptime(), some of the formats are new or have been extended for efficiency reasons. These formats are marked with "(*)". The fast parsers parse_date_time2() and fast_strptime() accept only formats marked with "(!)".

a

Abbreviated weekday name in the current locale. (Also matches full name)

A

Full weekday name in the current locale. (Also matches abbreviated name).

You don't need to specify a and A formats explicitly. Wday is automatically handled if preproc_wday = TRUE

b (!)

Abbreviated or full month name in the current locale. The C parser currently understands only English month names.

B (!)

Same as b.

d (!)

Day of the month as decimal number (01--31 or 0--31)

H (!)

Hours as decimal number (00--24 or 0--24).

I (!)

Hours as decimal number (01--12 or 1--12).

j

Day of year as decimal number (001--366 or 1--366).

q (!*)

Quarter (1--4). The quarter month is added to the parsed month if m format is present.

m (!*)

Month as decimal number (01--12 or 1--12). For parse_date_time. As a lubridate extension, also matches abbreviated and full months names as b and B formats. C parser understands only English month names.

M (!)

Minute as decimal number (00--59 or 0--59).

p (!)

AM/PM indicator in the locale. Normally used in conjunction with I and not with H. But the lubridate C parser accepts H format as long as hour is not greater than 12. C parser understands only English locale AM/PM indicator.

S (!)

Second as decimal number (00--61 or 0--61), allowing for up to two leap-seconds (but POSIX-compliant implementations will ignore leap seconds).

OS

Fractional second.

U

Week of the year as decimal number (00--53 or 0--53) using Sunday as the first day 1 of the week (and typically with the first Sunday of the year as day 1 of week 1). The US convention.

w

Weekday as decimal number (0--6, Sunday is 0).

W

Week of the year as decimal number (00--53 or 0--53) using Monday as the first day of week (and typically with the first Monday of the year as day 1 of week 1). The UK convention.

y (!*)

Year without century (00--99 or 0--99). In parse_date_time() also matches year with century (Y format).

Y (!)

Year with century.

z (!*)

ISO8601 signed offset in hours and minutes from UTC. For example -0800, -08:00 or -08, all represent 8 hours behind UTC. This format also matches the Z (Zulu) UTC indicator. Because base::strptime() doesn't fully support ISO8601 this format is implemented as an union of 4 orders: Ou (Z), Oz (-0800), OO (-08:00) and Oo (-08). You can use these four orders as any other but it is rarely necessary. parse_date_time2() and fast_strptime() support all of the timezone formats.

Om (!*)

Matches numeric month and English alphabetic months (Both, long and abbreviated forms).

Op (!*)

Matches AM/PM English indicator.

r (*)

Matches Ip and H orders.

R (*)

Matches HM andIMp orders.

T (*)

Matches IMSp, HMS, and HMOS orders.

Note

parse_date_time() (and the derivatives ymd(), ymd_hms(), etc.) relies on a sparse guesser that takes at most 501 elements from the supplied character vector in order to identify appropriate formats from the supplied orders. If you get the error All formats failed to parse and you are confident that your vector contains valid dates, you should either set exact argument to TRUE or use functions that don't perform format guessing (fast_strptime(), parse_date_time2() or base::strptime()).

For performance reasons, when timezone is not UTC, parse_date_time2() and fast_strptime() perform no validity checks for daylight savings time. Thus, if your input string contains an invalid date time which falls into DST gap and lt = TRUE you will get an POSIXlt object with a non-existent time. If lt = FALSE your time instant will be adjusted to a valid time by adding an hour. See examples. If you want to get NA for invalid date-times use fit_to_timeline() explicitly.

See Also

base::strptime(), ymd(), ymd_hms()

Aliases

• parse_date_time
• parse_date_time2
• fast_strptime

Examples

# NOT RUN {
## ** orders are much easier to write **
x <- c("09-01-01", "09-01-02", "09-01-03")
parse_date_time(x, "ymd")
parse_date_time(x, "y m d")
parse_date_time(x, "%y%m%d")
#  "2009-01-01 UTC" "2009-01-02 UTC" "2009-01-03 UTC"

## ** heterogeneous date-times **
x <- c("09-01-01", "090102", "09-01 03", "09-01-03 12:02")
parse_date_time(x, c("ymd", "ymd HM"))

## ** different ymd orders **
x <- c("2009-01-01", "02022010", "02-02-2010")
parse_date_time(x, c("dmY", "ymd"))
##  "2009-01-01 UTC" "2010-02-02 UTC" "2010-02-02 UTC"

## ** truncated time-dates **
x <- c("2011-12-31 12:59:59", "2010-01-01 12:11", "2010-01-01 12", "2010-01-01")
parse_date_time(x, "Ymd HMS", truncated = 3)

## ** specifying exact formats and avoiding training and guessing **
parse_date_time(x, c("%m-%d-%y", "%m%d%y", "%m-%d-%y %H:%M"), exact = TRUE)
parse_date_time(c('12/17/1996 04:00:00','4/18/1950 0130'),
                c('%m/%d/%Y %I:%M:%S','%m/%d/%Y %H%M'), exact = TRUE)

## ** quarters and partial dates **
parse_date_time(c("2016.2", "2016-04"), orders = "Yq")
parse_date_time(c("2016", "2016-04"), orders = c("Y", "Ym"))

## ** fast parsing **
# }
# NOT RUN {
  options(digits.secs = 3)
  ## random times between 1400 and 3000
  tt <- as.character(.POSIXct(runif(1000, -17987443200, 32503680000)))
  tt <- rep.int(tt, 1000)

  system.time(out <- as.POSIXct(tt, tz = "UTC"))
  system.time(out1 <- ymd_hms(tt)) # constant overhead on long vectors
  system.time(out2 <- parse_date_time2(tt, "YmdHMOS"))
  system.time(out3 <- fast_strptime(tt, "%Y-%m-%d %H:%M:%OS"))

  all.equal(out, out1)
  all.equal(out, out2)
  all.equal(out, out3)
# }
# NOT RUN {
## ** how to use `select_formats` argument **
## By default %Y has precedence:
parse_date_time(c("27-09-13", "27-09-2013"), "dmy")

## to give priority to %y format, define your own select_format function:

my_select <-   function(trained, drop=FALSE, ...){
   n_fmts <- nchar(gsub("[^%]", "", names(trained))) + grepl("%y", names(trained))*1.5
   names(trained[ which.max(n_fmts) ])
}

parse_date_time(c("27-09-13", "27-09-2013"), "dmy", select_formats = my_select)

## ** invalid times with "fast" parsing **
parse_date_time("2010-03-14 02:05:06",  "YmdHMS", tz = "America/New_York")
parse_date_time2("2010-03-14 02:05:06",  "YmdHMS", tz = "America/New_York")
parse_date_time2("2010-03-14 02:05:06",  "YmdHMS", tz = "America/New_York", lt = TRUE)
# }