printing of POSIXct should (could?) include tz info if it's there

[MichaelChirico]

DT = data.table(
  t1 = as.POSIXct('2018-05-01 12:34:56', tz = 'UTC'),
  t2 = as.POSIXct('2018-05-01 12:34:56', tz = 'Asia/Singapore')
)
DT
#                     t1                  t2
# 1: 2018-05-01 12:34:56 2018-05-01 12:34:56
DT$t1
# [1] "2018-05-01 12:34:56 UTC"
DT$t2
# [1] "2018-05-01 12:34:56 +08"

The printed output makes t1 and t2 seem identical, but they're not.

The same problem applies to data.frames, to be fair:

setDF(copy(DT))[]
#                    t1                  t2
# 1 2018-05-01 12:34:56 2018-05-01 12:34:56

Probably timezone printing should be on by default due to the above, but at least there should be an option.

[jangorecki]

default format probably best something like +00:00, less dependent on timezone dictionaries in OSes