将 R fread 中的字符日期转换为显示四位数年份格式

Question

I have a csv file which shows date as 14-Mar-20 . Its a Date-Month-Year format. But in background it is showing as 3/14/2020.

When I try to do fread this file into R it comes as a character format 14-Mar-20.I converted this to date as as.Date(x, format("%d-%h-%Y).

The issue is, In R the date shows the year as "20" (Two digits). I want to read the data as four digit year into R. I don't want to add string 20 to make it 2020 as there can also have years like 1948. No amount of formatting helps with Year as %Y.

Is there a way to read csv file such that the date comes as 14/Mar/2020 or a way in R to make the years into four digit without string add of 20 to year?

Sample Data

c("12-Dec-14", "19-Dec-14", "12-Dec-14", "19-Dec-14", "12-Dec-14", 
"26-Dec-14")

Expected Output:

12-12-2014, 19-Dec-2014....

Note: In csv file it is stores as 12/12/2014 but formatted to show as 12-Dec-14. So when I pull the data in R it comes as 12-Dec-14

Answer 1

Maybe this could help

> strftime(as.Date(d,format = "%d-%b-%y"),format = "%d-%b-%Y")
[1] "12-Dec-2014" "19-Dec-2014" "12-Dec-2014" "19-Dec-2014" "12-Dec-2014"
[6] "26-Dec-2014"

Data

d <- c("12-Dec-14", "19-Dec-14", "12-Dec-14", "19-Dec-14", "12-Dec-14", 
"26-Dec-14")

Answer 2

You want to use %y.

From the documentation of strptime() :

Year without century (00–99). On input, values 00 to 68 are prefixed by 20 and 69 to 99 by 19 – that is the behaviour specified by the 2018 POSIX standard, but it does also say 'it is expected that in a future version the default century inferred from a 2-digit year will change'.

Answer 3

You can use as.Date to convert dates into date class.

x <- c("12-Dec-14", "19-Dec-14", "12-Dec-14", "19-Dec-14", "12-Dec-14",  "26-Dec-14")
x1 <- as.Date(x, '%d-%b-%y')
x1
#[1] "2014-12-12" "2014-12-19" "2014-12-12" "2014-12-19" "2014-12-12" "2014-12-26"

If you want data in specific format use format on date values.

x2 <- format(x1, '%d-%b-%Y')
x2
#[1] "12-Dec-2014" "19-Dec-2014" "12-Dec-2014" "19-Dec-2014" "12-Dec-2014" "26-Dec-2014"