I'm importing data from Excel and then trying to manipulate dates and times in R and it's giving me SUCH A HEADACHE. In the Excel file, one column contained a date and time, and another column contained a different time for that same day. The data in R looks basically like this example:
mydata <- data.frame(DateTime1 = as.POSIXct(c("2014-12-13 04:56:00",
"2014-12-13 09:30:00",
"2014-12-13 11:30:00",
"2014-12-13 13:30:00"),
origin = "1970-01-01", tz = "GMT"),
Time2 = c(0.209, 0.209, 0.715, 0.715))
I'd like to have a new column in POSIXct format with the date and the 2nd time, and I can't get that to work. I've tried:
mydata$DateTime2 <- as.POSIXct(as.numeric(as.Date(mydata$DateTime1)
+ mydata$Time2), origin = "1970-01-01",
tz = "GMT")
but that gives me dates and times close to 1/1/1970.
This is more convoluted, but one thing that has worked in other similiar situations that I've also tried is:
library(lubridate)
mydata$DateTime2 <- ymd_hms(format(as.POSIXct(as.Date(mydata$DateTime1) +
mydata$Time2,
origin = "1899-12-30", tz = "GMT")))
but that gives me dates and times that are off by 8 hours. That time difference makes me think that the problem is the time zone since I'm on Pacific Standard Time, but I set it to GMT both in the input data and when trying to convert! What gives? I'm hesitant to just add 8 hours to everything because of daylight savings time complications.
Really, both of the attempts I'm listing here seem to have problems with interconversion, i.e., if you start with a POSIXct object and convert it to numeric and then convert it back again to POSIXct, you should end up back where you started and you don't. Similarly, if you start with the time zone being GMT and then you add something that also is set to have the time zone as GMT, then you shouldn't have a problem with things somewhere mysteriously getting converted to the system time zone.
Advice?
I found an answer based on chris holbrook's answer here: How do you convert dates/times from one time zone to another in R?
This worked:
mydata$DateTime2 <- as.POSIXct(as.Date(mydata$DateTime1) +
mydata$Time2)
attributes(mydata$DateTime2)$tzone <- "GMT"
#MichaelChirico and I were correct that the time zone was the problem. I'm still not sure why, but the time zone for DateTime2 was apparently PST. It didn't list "PST" when I checked str(mydata$DateTime2), but based on the time difference, it must have been, in fact, PST until I set the attributes. Crazy. It did that even though DateTime1 was GMT.
Related
I am working on Rstudio and I'm trying to retrieve time from a date-time column. for example, the date-time column looks like this in my vector '2020-01-01 00:33:03'. This is only one observation I have in the column I want to extract information from.
Anyway, When I apply strftime('2020-01-01 00:33:03', '%H') and want to extract hours in this case. The function does not give me the correct hour which is in this cases 12 AM instead it gives me 16. I am not sure if there is anything I should specify further. This is New York Time idk if that helps.
I really appreciate any feedback or if there is any other functions/packages that I should use other than this one.
new york should be eastern time zone. Have you tried to first give it a timezone before acquiring the hour?
t <- strptime( '2020-01-01 00:33:03',
format = "%Y-%m-%d %H:%M:%OS",
tz = "EST")
strftime(t, '%H')
You can acquire your actual tz also with Sys.timezone(location = TRUE)
Newbie here, first post (please be gentle). I have been trying to resolve this for several hours, so finally decided time to ask advice.
I have a large spreadsheet which I am importing with readxl. It contains one column with date (format dd/mm/yyyy) and several time columns in format hh:mm as can be seen: excel
Essentially I want to be able to import both time and date columns and combine them, so that I can then do some other calculations, like time elapsed.
If I import letting R guess the col-types, it converts the times to POSIXct, but these then have a date on 1899 attached to them: R_POSIXct
If I force readxl to assign the time column to numeric, I get a decimal (e.g. 0.315972222 for 07:35), which then tried converting using similar syntax to
format(as.POSIXct(Sys.Date() + 0.315972222), "%Y-%m-%d %H:%M:%S", tz="UTC")
i.e.
df$datetime <- format(as.POSIXct(df$date + df$time), "%Y-%m-%d %H:%M", tz="UTC")
which results in the correct date, but with a time of 00:00, not the time it is passed.
I have tried searching here and found posts to be not quite the same question (e.g. Combining date and time columns into dd/mm/yyyy hh:mm), and have read widely, including about about lubridate, but as I'm only 6 months into R, am finding some explanations a bit cryptic.
Suggestions or ignposting appreciated (if there are solutions I haven't found)
If you subtract the number of days between 1899-01-01 and 1970-01-01 and then multiply that (shifted) Excel numeric value by 3600 you should come close to the number of seconds since start of 1970. You could then convert to POSIXct with as.POSIXct( x, origin="1970-01-01"). That does seem to be "the hard way", however
It would be far easier and probably more accurate to convert the date-times to YYYY-MM-DD H:M:S format and then export as csv to be imported into R as text. There is a "POSIXct" colClasses argument to read.csv, although it doesn't handle separate columns of date and time. For that you would be advised to import as character values and then paste the dates and times. Then watch you format strings for as.POSIXct. The dd/mm/yyyy "format" would be specified by "%d/%m/%Y".
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"))