why converting time zone not working with as.POSIXct... [R]

Question

I've read this and it says as.POSIXct is always UTC internally. No wonder I got

> time1 = as.POSIXct('2015-10-25 10:15:13 UTC')
> time1
[1] "2015-10-25 10:15:13 EDT"
# missing tz causes coercion (not converting!) to computer's tz. 
# (I'm in EDT Boston and calculating some data in Dubai time)


> time1 = as.POSIXct('2015-10-25 10:15:13 UTC', tz = 'UTC', usetz = T)
> time1
[1] "2015-10-25 10:15:13 UTC"

# not work
> as.POSIXct(time1, tz = 'Asia/Dubai', usetz = T)
[1] "2015-10-25 10:15:13 UTC"

# works but the result is character
> format(time1, tz = 'Asia/Dubai', usetz = T)
[1] "2015-10-25 14:15:13 GST"
> class(format(time1, tz = 'Asia/Dubai', usetz = T))
[1] "character"

I can use format, but it yields character and I can't use it in plotting something vs time. How can I plot with local time?

hi @DavidArenburg thanks man - i looks it does - see update in OP pls — YJZ, Oct 26 '15 at 11:32
You could also just do `as.POSIXct(format(time1, tz = 'Asia/Dubai', usetz = TRUE), tz = 'Asia/Dubai')` — David Arenburg, Oct 26 '15 at 11:35

YJZ · Answer 1 · 2015-10-27T16:28:34.537

tried something and this works:

> library(lubridate)
> time1 = as.POSIXct('2015-10-25 10:15:13 UTC', tz = 'UTC', usetz = T)
> time1
[1] "2015-10-25 10:15:13 UTC"
> force_tz(time1 + 3600*4, tz = 'Asia/Dubai')
[1] "2015-10-25 14:15:13 GST"
> class(force_tz(time1 + 3600*4, tz = 'Asia/Dubai'))
[1] "POSIXct" "POSIXt"

Also doable with Rbase with a lightly longer syntax (thanks @David Arenburg)

> time1 = as.POSIXct('2015-10-25 10:15:13 UTC', tz = 'UTC', usetz = T)
> time1
[1] "2015-10-25 10:15:13 UTC"
> as.POSIXct(format(time1, tz = 'Asia/Dubai', usetz = T), tz = 'Asia/Dubai', usetz = T)
[1] "2015-10-25 14:15:13 GST"

why converting time zone not working with as.POSIXct... [R]

1 Answers1