How to extract correct date from POSIXct element? [duplicate]

问题

This question already has answers here:

Date conversion from POSIXct to Date in R (3 answers)

Closed 4 years ago.

How can I get the correct date from the first column in my code?

test <- data.frame(posixdate = c("2013-05-01 00:59:00", "2013-05-01 01:59:00", "2013-05-01 02:59:00", "2013-05-01 03:59:00"))
test$posixdate <- as.POSIXct(test$posixdate, format="%Y-%m-%d %H:%M:%S" )
test$date <- as.Date(test$posixdate)

The above code results in:

  posixdate           date
1 2013-05-01 00:59:00 2013-04-30
2 2013-05-01 01:59:00 2013-04-30
3 2013-05-01 02:59:00 2013-05-01
4 2013-05-01 03:59:00 2013-05-01

The first two dates are not correct. What did I do wrong? If as.Date() is not the right function, how could I get the date (without hours, minutes, seconds) alternatively?

Thanks in advance!

回答1:

the problem is the timezone

try your timezone (probably not GMT)

test$date2 <- as.Date(test$posixdate, "GMT")

and read this post

回答2:

Try with lubridate package. It works for me.

library(lubridate)

as.Date(ymd_hms(test$posixdate))

[1] "2013-05-01" "2013-05-01" "2013-05-01" "2013-05-01"

来源：https://stackoverflow.com/questions/29206881/how-to-extract-correct-date-from-posixct-element