如何使用R转换日期

Question

Currently, I have a lot of data. Associated with the data, I also have dates. Unfortunately, the dates are in the following format (day (Monday-Sunday), month (January-December) date (1-31) Hour:Minute:Second timezone Year). I would like to convert this into just Month/Day(1-31)/Year. Following is the sample data.

created_data
Sat Jun 20 23:45:03 +0000 2015
Sat Jun 20 23:45:06 +0000 2015
Sat Jun 20 23:45:06 +0000 2015
Sat Jun 20 23:45:08 +0000 2015
Sat Jun 20 23:45:11 +0000 2015
Sat Jun 20 23:45:13 +0000 2015
Sat Jun 20 23:45:14 +0000 2015
Sat Jun 20 23:45:15 +0000 2015

This is currently in the form of a dataframe. The format in which I am trying to see the dataframe is the following:

Results
Jun 20 2015
Jun 20 2015
Jun 20 2015
Jun 20 2015
Jun 20 2015
Jun 20 2015
Jun 20 2015
Jun 20 2015 

Following is the code that I have tried but the result was just NA

strptime(x = created_data, format = "%m/%d/%Y")

Result = NA

Answer 1

First you have to convert your character string to something that R knows how to deal with such as a POSIXct object.

Given your format you can do as.POSIXct(created_data), format="%a %b %d %X %z %Y")

Once it is in that format you can convert it back to a character string of the format you want using format such as...

format(as.POSIXct(created_data, format="%a %b %d %X %z %Y"), format = "%Y/%m/%d")

Answer 2

The following should work, assuming the datetimes are stored in a character vector.

library("stringr")
library("dplyr")

dates <- c("Sat Jun 20 23:45:03 +0000 2015", 
           "Sat Jun 20 23:45:06 +0000 2015", 
           "Sat Jun 20 23:45:06 +0000 2015", 
           "Sat Jun 20 23:45:08 +0000 2015", 
           "Sat Jun 20 23:45:11 +0000 2015", 
           "Sat Jun 20 23:45:13 +0000 2015", 
           "Sat Jun 20 23:45:14 +0000 2015", 
           "Sat Jun 20 23:45:15 +0000 2015")

str_split_fixed(dates, pattern = " ", n=6) %>% 
  as.data.frame() %>%
  mutate(new.date = as.Date(paste(V2, V3, V6), format = "%b %d %Y"))

The basic idea being to split the string into its individual pieces using str_split_fixed() , then recombine the pieces in as.Date()

Answer 3

Just a base R solution without other packages.

 x <- "Sat Jun 20 23:45:03 +0000 2015"
 x1 <- format(strptime(x, "%a %b %d %H:%M:%S %z %Y", tz = "GMT"), "%b %d %Y")
 x1
[1] "Jun 20 2015"