lubridate::ymd

ymd(..., quiet = FALSE, tz = NULL, locale = Sys.getlocale('LC_TIME'), truncated = 0)

Returns: Date | POSIXct · Updated March 20, 2026 · Tidyverse

r lubridate dates

ymd() parses dates in year-month-day order from character strings or numbers. It is the most commonly used parser in lubridate because machine-generated date formats — CSV exports, database dumps, API responses — tend to follow this arrangement. The function auto-detects separators (hyphens, slashes, spaces, or none) and handles mixed formats within a single vector without you specifying a format string.

Syntax

ymd(..., quiet = FALSE, tz = NULL, locale = Sys.getlocale("LC_TIME"), truncated = 0)

ymd() is part of a family of parsers sharing the same signature. The function name encodes the element order:

Function	Element order	Example input	Parsed as
`ymd()`	year, month, day	`"2009-01-02"`	2009-01-02
`ydm()`	year, day, month	`"2009-02-01"`	2009-01-02
`mdy()`	month, day, year	`"01-02-2009"`	2009-01-02
`myd()`	month, year, day	`"01-2009-02"`	2009-01-02
`dmy()`	day, month, year	`"02-01-2009"`	2009-01-02
`dym()`	day, year, month	`"02-2009-01"`	2009-01-02
`yq()`	year, quarter	`"2014.2"`	2014-04-01
`ym()`	year, month	`"2012-06"`	2012-06-01
`my()`	month, year	`"Jan 2009"`	2009-01-01

Use ymd_hms() (and variants) when you need to parse times as well.

Parameters

Parameter	Type	Default	Description
`...`	character or numeric	Required	A vector of suspected dates. Each element may use a different format.
`quiet`	logical	`FALSE`	Suppress parsing progress messages. Set to `TRUE` for large vectors.
`tz`	character	`NULL`	Timezone. `NULL` returns a `Date`; any other value returns `POSIXct`.
`locale`	character	`Sys.getlocale("LC_TIME")`	Locale for parsing month names. Rarely needs changing.
`truncated`	integer	`0`	Allow N rightmost components to be missing. `truncated = 2` parses `"2012"` as `"2012-01-01"`.

Return Value

Returns a Date object by default. When tz is set, returns a POSIXct object with the specified timezone instead.

ymd("20090101")
# [1] "2009-01-01"
# class: Date

ymd("20090101", tz = "UTC")
# [1] "2009-01-01 UTC"
# class: POSIXct POSIXt

Examples

Basic usage

library(lubridate)

# From character — any separator works
ymd("2009-01-01")
# [1] "2009-01-01"

# From numeric — compact form, no separator needed
ymd(20090101)
# [1] "2009-01-01"

Multiple dates at once

# Multiple arguments — each argument becomes one element
ymd(090101, 90102)
# [1] "2009-01-01" "2009-01-02"

# Single vector with mixed formats
ymd(c(20090101, "2009-01-02", "2009 01 03", "2009-1-4"))
# [1] "2009-01-01" "2009-01-02" "2009-01-03" "2009-01-04"

Truncated dates

When some components are missing, set truncated to allow the parser to fill in defaults (day and month default to 01):

# Year and month only — day becomes 01
ymd("2012-06", truncated = 1)
# [1] "2012-06-01"

# Year only — both month and day become 01
ymd("2012", truncated = 2)
# [1] "2012-01-01"

With timezone

# POSIXct when tz is specified
ymd("2009-01-01", tz = "America/New_York")
# [1] "2009-01-01 EST"

Using with dplyr

library(dplyr)

events <- data.frame(
  date_chr = c("20240315", "20240316", "20240317"),
  event = c("login", "purchase", "logout")
)

events %>%
  mutate(date = ymd(date_chr))
#       date_chr   event       date
# 1  20240315    login 2024-03-15
# 2  20240316 purchase 2024-03-16
# 3  20240317   logout 2024-03-17

Common problems

“All formats failed to parse”: When the input has too many NA values or non-date strings, lubridate cannot guess the format reliably. Switch to parse_date_time() with an explicit format list.

Two-digit years: ymd("990101") is parsed as 2099-01-01 in current lubridate. The century interpretation has changed across lubridate versions — do not rely on it for two-digit years without explicit conversion.

NA with warning: Individual unparseable elements return NA with a warning listing how many failed. This is not an error — check is.na() on the result to find the problem elements.