I have a table (tags) with a column for timestamp (ts), which is formatted as seconds since 1 Jan, 1970 GMT. I'm trying to create a date column that converts the timestamp from seconds to date and time EST.
The suggested code for R was:
tags$date<-strptime(tags$ts, "%Y-%m-%d")
tags$date<-as.POSIXct(tags$date)
But when I do this, tags$date comes up as NA. Any suggestions for what I might be doing wrong? Thanks.
You should us as.POSIXct function instead:
tags$date <- as.POSIXct(tags$ts, origin="1970-01-01", tz="US/New York")
strptime converts between character representations and dates not between timestamp and dates.
Here's a lubridate version. When we use as_datetime we don't need to explicitly specify an origin as it defaults to the desired origin.
lubridate::as_datetime(1507119276, tz='EST')
# [1] "2017-10-04 07:14:36 EST"
Unix time is 1435617000.
as.Date(1435617000,origin="01-01-1970")
[1] "3930586-11-23"
Which is wrong. I'm trying to (a) get the correct date, which, per epoch converter is GMT: Mon, 29 Jun 2015 22:30:00 GMT.
How do I get R to tell me the month, day, year, hour, minute & second? Thank you.
I think the reason why that happen is because as.Date converts arguments to class date objects. In this case you do not need a date but a class POSIXct object because your input, the x vector, contains other informations that as.Date is not able to manage. Another problem that even with the right function could appear, is that if when you do not specify the right time zone with the tz argument (except the case where your time zone is the same as the original time).
The following code does the job.
x <- 1435617000
as.POSIXct(x, origin = "1970-01-01", tz ="GMT")
[1] "2015-06-29 22:30:00 GMT"
Use as.Date
Just in the case you wanted only the date but you have a complete Unix time like x, you have to just divide by 86400 (which is the number of seconds in a day!) to get only the right date.
as.Date(x/86400L, origin = "1970-01-01")
[1] "2015-06-29"
Another important detail
The origin argument has to be supplied with YYYY-MM-DD and not like you did DD-MM-YYYY I am not sure but I think that the former is the only accepted and correct way.
I am trying to convert UTC time to local standard time. I have found many functions which convert to Local Daylight Time, but I was not successful in getting the standard time. Right now, I have the following code which converts to local daylight time at my specific timezone:
pb.date <- as.POSIXct(date,tz="UTC")
format(pb.date, tz="timeZone",usetz=TRUE)
I would appreciate any help.
First, POSIXct date-times are always UCT internally. The print.POSIXt and format.POSIXt methods will appropriately make the TZ shift on output from their internal representations:
pb.date <- as.POSIXct(Sys.Date())
Sys.Date()
#[1] "2015-07-09"
So that was midnight of the current date in Greenwich:
format(pb.date, tz="America/Los_Angeles",usetz=TRUE)
#[1] "2015-07-08 17:00:00 PDT"
When it's midnight in Greenwich, it's 5PM Daylight Time in the previous day on the Left Coast of the US. You need to use the correct character values for your TZ (and your OS) both of which at the moment are unspecified.
The US Pacific timezone is 8 hours behind GMT (in winter months) so you can use a timezone that is Standard/Daylight-agnostic:
> format(pb.date,usetz=TRUE, tz="Etc/GMT+8")
[1] "2015-07-08 16:00:00 GMT+8"
(Notice the reversal of + with "behind" and - with "ahead".)
I know this question has an accepted answer, but in case anyone comes along and this can help. I needed a function to convert UTC times to MTN time (Server is in UTC, we operate in MTN).
Not sure why, but needed to force it to UTC/GMT first and the convert it to MTN. However it does work
mtn_ts = function(utcTime){
library(lubridate)
toTz = "us/mountain"
utcTime = force_tz(utcTime,tzone= 'GMT')
dt = as.POSIXct(format(utcTime,tz = toTz,origin ='GMT', usetz=TRUE))
dt = force_tz(dt,tzone= toTz)
return(dt)
}
mtn_ts(as.POSIXct("2021-09-27 14:48:51.000000000"))
I am trying to convert UTC time to local standard time. I have found many functions which convert to Local Daylight Time, but I was not successful in getting the standard time. Right now, I have the following code which converts to local daylight time at my specific timezone:
pb.date <- as.POSIXct(date,tz="UTC")
format(pb.date, tz="timeZone",usetz=TRUE)
I would appreciate any help.
First, POSIXct date-times are always UCT internally. The print.POSIXt and format.POSIXt methods will appropriately make the TZ shift on output from their internal representations:
pb.date <- as.POSIXct(Sys.Date())
Sys.Date()
#[1] "2015-07-09"
So that was midnight of the current date in Greenwich:
format(pb.date, tz="America/Los_Angeles",usetz=TRUE)
#[1] "2015-07-08 17:00:00 PDT"
When it's midnight in Greenwich, it's 5PM Daylight Time in the previous day on the Left Coast of the US. You need to use the correct character values for your TZ (and your OS) both of which at the moment are unspecified.
The US Pacific timezone is 8 hours behind GMT (in winter months) so you can use a timezone that is Standard/Daylight-agnostic:
> format(pb.date,usetz=TRUE, tz="Etc/GMT+8")
[1] "2015-07-08 16:00:00 GMT+8"
(Notice the reversal of + with "behind" and - with "ahead".)
I know this question has an accepted answer, but in case anyone comes along and this can help. I needed a function to convert UTC times to MTN time (Server is in UTC, we operate in MTN).
Not sure why, but needed to force it to UTC/GMT first and the convert it to MTN. However it does work
mtn_ts = function(utcTime){
library(lubridate)
toTz = "us/mountain"
utcTime = force_tz(utcTime,tzone= 'GMT')
dt = as.POSIXct(format(utcTime,tz = toTz,origin ='GMT', usetz=TRUE))
dt = force_tz(dt,tzone= toTz)
return(dt)
}
mtn_ts(as.POSIXct("2021-09-27 14:48:51.000000000"))
I have time series data from 1974-2013 with a column for datetimeUTC (YYYY-MM-DD hh:mm +0000), and a column for the timezones in Olson format (e.g., Canada/Pacific, Canada/Eastern). I can convert the whole UTCdatetime column to a common timezone like this:
dataset$datetimeEST <- strptime(
dataset$datetimeUTC, format="%Y-%m-%d %H:%M:%S%z", tz="Canada/Eastern"
)
How do I convert datetimeUTC to datetimeLOCAL, given the corresponding timezone in each row?
Let me back up a bit. I have data from across the country (6 timezones) formatted in ISO8601 representation for 1974-2013. The timestamps are in local standard time throughout the year (i.e. DST is disregarded even if civilian time in the region observes DST). I need to do datetime calculations which are probably safest to do in UTC time, so that's easy. But, I also need to pull data for specific civil time periods, taking into account DST, and do calculations and plots (e.g., all the data for rush hour at locations across all 6 timezones) for that subsetted data.
The datetimeCLOCKTIME that I calculated below appears to be doing what I want for plotting, but gives the wrong answer when doing datetime calculations because it stored the datetime in the timezone of my local machine without having actually converted the time. The solution offered by #thelatemail is what I'm looking for, but I haven't been able to get it to work in Windows on the test dataset for 2012 (see below). Also, I was using strptime which converts to POXITlt, and his solution is in POXITct. I'm new to R, so any help would be infinitely appreciated.
Test dataset:
dataset <- data.frame (timestampISO8601 = c("2012-04-25T22:00:00-08:00","2012-04-25T22:15:00-08:00","2012-04-25T22:30:00-08:00","2012-04-25T22:45:00-08:00","2012-04-25T23:00:00-08:00","2012-04-25T23:15:00-08:00","2012-04-25T23:30:00-08:00","2012-04-25T23:45:00-08:00","2012-04-26T00:00:00-08:00","2012-04-26T00:15:00-08:00","2012-04-26T00:30:00-08:00","2012-04-26T00:45:00-08:00","2012-04-26T01:00:00-08:00","2012-04-26T01:15:00-08:00","2012-04-26T01:30:00-08:00","2012-04-26T01:45:00-08:00","2012-04-26T02:00:00-08:00","2012-04-25T22:00:00-03:30","2012-04-25T22:15:00-03:30","2012-04-25T22:30:00-03:30","2012-04-25T22:45:00-03:30","2012-04-25T23:00:00-03:30","2012-04-25T23:15:00-03:30","2012-04-25T23:30:00-03:30","2012-04-25T23:45:00-03:30","2012-04-26T00:00:00-03:30","2012-04-26T00:15:00-03:30","2012-04-26T00:30:00-03:30","2012-04-26T00:45:00-03:30","2012-04-26T01:00:00-03:30","2012-04-26T01:15:00-03:30","2012-04-26T01:30:00-03:30","2012-04-26T01:45:00-03:30","2012-04-26T02:00:00-03:30"), olson = c("Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Pacific","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland","Canada/Newfoundland"), value = c(0,0,1,2,5,11,17,19,20,19,17,11,5,2,1,0,0,-3,-3,-2,-1,2,8,14,16,17,16,14,8,2,-1,-2,-3,-3), stringsAsFactors=FALSE)
Remove the ":" from the UTC offset. (R is expecting the format nnnn for the UTC offset):
dataset$timestampR<- paste(substr(dataset$timestampISO8601,1,22),substr(dataset$timestampISO8601,24,25),sep="")
When converting to UTC time, R defaults to -ve for the UTC offset, making -ve offsets in the timestamps positive:
dataset$datetimeUTC <- strptime(dataset$timestampR, format="%Y-%m-%dT%H:%M:%S%z", tz="UTC")
When converting to MACHINE time like this, R reads the input time and converts it to the time in the timezone of the local machine - in my case, this is Canada/Eastern:
dataset$datetimeMACHINE <- strptime(dataset$timestampR, format="%Y-%m-%dT%H:%M:%S%z")
When converting to CLOCKTIME time like this, R reads the input time and assigns the time zone of the local machine (currently EDT on my machine) without doing any time conversions:
dataset$datetimeCLOCKTIME <- strptime(dataset$timestampR,format="%Y-%m-%dT%H:%M:%S")
See the structure of the dataset:
str(dataset)
Plotting behaviours are different
library(ggplot2)
qplot(data=dataset,x=datetimeUTC,y=value)
qplot(data=dataset,x=datetimeMACHINE,y=value)
qplot(data=dataset,x=datetimeCLOCKTIME,y=value)
Calculation results differ. Incorrect calculation result for datetimeCLOCKTIME:
range (dataset$datetimeUTC)
range (dataset$datetimeMACHINE)
range (dataset$datetimeCLOCKTIME)
dataset$datetimeUTC[34] - dataset$datetimeUTC[1]
dataset$datetimeMACHINE[34] - dataset$datetimeMACHINE[1]
dataset$datetimeCLOCKTIME[34] - dataset$datetimeCLOCKTIME[1]
You could format back and forth a bit to get a local time representation in a character format. E.g.:
dataset <- data.frame(
datetimeUTC=c("2014-01-01 00:00 +0000","2014-01-01 00:00 +0000"),
olson=c("Canada/Eastern", "Canada/Pacific"),
stringsAsFactors=FALSE
)
# datetimeUTC olson
#1 2014-01-01 00:00 +0000 Canada/Eastern
#2 2014-01-01 00:00 +0000 Canada/Pacific
dataset$localtime <- with(dataset,
mapply(function(dt,ol) format(
as.POSIXct(dt,"%Y-%m-%d %H:%M %z",tz=ol),
"%Y-%m-%d %H:%M %z"),
datetimeUTC, olson
)
)
# datetimeUTC olson localtime
#1 2014-01-01 00:00 +0000 Canada/Eastern 2013-12-31 19:00 -0500
#2 2014-01-01 00:00 +0000 Canada/Pacific 2013-12-31 16:00 -0800
If you have only two time zones to convert to and know the difference in time between UTC and those two. Using #thelatemail's dataset
transform(dataset,
localtime=as.POSIXct(datetimeUTC, "%Y-%m-%d %H:%M %z")-
c(5*3600,8*3600)[as.numeric(factor(olson))])
# datetimeUTC olson localtime
#1 2014-01-01 00:00 +0000 Canada/Eastern 2013-12-31 19:00:00
#2 2014-01-01 00:00 +0000 Canada/Pacific 2013-12-31 16:00:00