Converting Numeric Time to Datetime Posixct Format in R

Converting numeric time to datetime POSIXct format in R

Try one of these depending on which time zone you want:

t.gmt <- as.POSIXct(3600 * (tdat - 974424), origin = '2011-03-01', tz = "GMT") 

t.local <- as.POSIXct(format(t.gmt))

Reconvert numeric date to POSIXct R

As the numeric vector is created from an object with time component, reconversion can also be in the same way i.e. first to POSIXct and then wrap with as.Date

as.Date(as.POSIXct(date1_num, origin = '1970-01-01'))
#[1] "2017-12-30"

How to convert date & time to numeric by using POSIXct and how to calculate the time?

Additionally, you can also use mdy_hm function from lubridate -

library(dplyr)
library(lubridate)

df <- df %>% mutate(across(c(starttime, stoptime), mdy_hm))

In base R, you can use as.POSIXct

df[1:2] <- lapply(df[1:2], as.POSIXct, format = "%m/%d/%Y %H:%M")

Changing the format from numeric to POSIXct object in R

This is not the most elegant solution, but it works

library(stringr)
library(dplyr)

example_data <- c("20121029 0", "20121029 100", "20121029 2100")

# Extract the times
times <- example_data %>% strsplit(. , " ") %>% sapply(. , "[", 2)
times <- str_pad(times, max(nchar(times)), side="right", pad="0")

# Extract just the dates
dates <- example_data %>% substr(., 1, 8)

# Combine date and time and convert to POSIXct
date_time <- paste(dates, times) %>% as.POSIXct(., format="%Y%m%d %H%M")

Convert numeric time format to POSIXlt

Break your numeric values to convert them all to seconds, and add that to a datetime for today:

x <- c(0.00,0.00,0.00,30.19,0.00,25.00,0.00,9.20,0.00,0.00)
as.POSIXct(format(Sys.Date()), tz="Australia/Darwin") + (floor(x)*60) + ((x-floor(x))*100)
# [1] "2017-07-05 00:00:00 ACST" "2017-07-05 00:00:00 ACST" "2017-07-05 00:00:00 ACST" "2017-07-05 00:30:19 ACST"
# [5] "2017-07-05 00:00:00 ACST" "2017-07-05 00:25:00 ACST" "2017-07-05 00:00:00 ACST" "2017-07-05 00:09:20 ACST"
# [9] "2017-07-05 00:00:00 ACST" "2017-07-05 00:00:00 ACST"

This is in Darwin time, ACST instead of AEST, but I gather that's what you want.

Convert numeric time in milliseconds to datetime with seconds with decimal value

With lubridate, using as_datetime

library(lubridate)
as_datetime(time/1000)
[1] "2021-10-08 16:01:17 UTC"

Note that the milliseconds are not printed in the console. If we need to print, then format with strftime or format (but it will not be a datetime object anymore)

strftime(as_datetime(time/1000), '%Y-%m-%d %H:%M:%OS3') 
#[1] "2021-10-08 11:01:17.772"

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Or without using any package, just specify it in as.POSIXct

as.POSIXct(time/1000, origin = '1970-01-01')
[1] "2021-10-08 11:01:17 CDT"

How to convert numeric time into date, time format in R

Big fan of parse_date_time from lubridate and the timetk package:

library(tidyverse)
library(lubridate)
library(timetk)

test %>%
  mutate(date = parse_date_time(paste(date, str_pad(time, 4, side = "left", pad = "0")), "YmdHM")) %>%
  select(-time) %>%
  tk_xts(silent = T)

                     price
1990-01-02 09:30:00 353.40
1990-01-02 09:31:00 353.25
1990-01-02 09:32:00 353.02
1990-01-02 09:33:00 352.97
1990-01-02 09:34:00 352.81
1990-01-02 09:35:00 352.74

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