Creating date/times

To get the current date or date-time

today()

## [1] "2021-01-24"

now()

## [1] "2021-01-24 23:54:54 EST"

Three ways to create a date/time:

From a string
From individual date-time components
From an existing date/time object

From a string

date_string = "2021-01-24"
class(date_string)

## [1] "character"

ymd(date_string)

## [1] "2021-01-24"

mdy("January 21st, 2021")

## [1] "2021-01-21"

dmy("24-January-2021")

## [1] "2021-01-24"

These functions also take unquoted numbers. This is the most concise way to create a single date/time object, as you might need when filtering date/time data. ymd() is short and unambiguous:

ymd(20210124)

## [1] "2021-01-24"

ymd(20210103)

## [1] "2021-01-03"

ydm(20210103)

## [1] "2021-03-01"

To create a date-time, add an underscore and one or more of “h”, “m”, and “s” to the name of the parsing function:

ymd_hms("2021-01-24 23:18:59")

## [1] "2021-01-24 23:18:59 UTC"

mdy_hm("01/24/2021 08:01")

## [1] "2021-01-24 08:01:00 UTC"

From individual components

library(tidyverse)

## -- Attaching packages --------------------------------------- tidyverse 1.3.0 --

## v ggplot2 3.3.3     v purrr   0.3.4
## v tibble  3.0.5     v dplyr   1.0.3
## v tidyr   1.1.2     v stringr 1.4.0
## v readr   1.4.0     v forcats 0.5.0

## -- Conflicts ------------------------------------------ tidyverse_conflicts() --
## x lubridate::as.difftime() masks base::as.difftime()
## x lubridate::date()        masks base::date()
## x dplyr::filter()          masks stats::filter()
## x lubridate::intersect()   masks base::intersect()
## x dplyr::lag()             masks stats::lag()
## x lubridate::setdiff()     masks base::setdiff()
## x lubridate::union()       masks base::union()

library(nycflights13)

flights %>% 
  select(year, month, day, hour, minute) %>% 
  head(10)

## # A tibble: 10 x 5
##     year month   day  hour minute
##    <int> <int> <int> <dbl>  <dbl>
##  1  2013     1     1     5     15
##  2  2013     1     1     5     29
##  3  2013     1     1     5     40
##  4  2013     1     1     5     45
##  5  2013     1     1     6      0
##  6  2013     1     1     5     58
##  7  2013     1     1     6      0
##  8  2013     1     1     6      0
##  9  2013     1     1     6      0
## 10  2013     1     1     6      0

To create a date/time from this sort of input, use make_date() for dates, or make_datetime() for date-times:

flights %>% 
  select(year, month, day) %>% 
  mutate(departure = make_datetime(year, month, day))

## # A tibble: 336,776 x 4
##     year month   day departure          
##    <int> <int> <int> <dttm>             
##  1  2013     1     1 2013-01-01 00:00:00
##  2  2013     1     1 2013-01-01 00:00:00
##  3  2013     1     1 2013-01-01 00:00:00
##  4  2013     1     1 2013-01-01 00:00:00
##  5  2013     1     1 2013-01-01 00:00:00
##  6  2013     1     1 2013-01-01 00:00:00
##  7  2013     1     1 2013-01-01 00:00:00
##  8  2013     1     1 2013-01-01 00:00:00
##  9  2013     1     1 2013-01-01 00:00:00
## 10  2013     1     1 2013-01-01 00:00:00
## # ... with 336,766 more rows

From other types

to switch between a date-time and a date

as_datetime(today())

## [1] "2021-01-24 UTC"

as_date(now())

## [1] "2021-01-24"

Lubridate package