posixct

I have a character datetime column in a file. I load the file (into a data.table ) and do things that require the column to be converted to POSIXct . I then need to write the POSIXct value back to file, but the datetime will not be the same (because it is printed incorrectly). This print/formatting issue is well known and has been discussed several times. I've read some posts describing this issue. The most authoritative answers I found are given in response to this question . The answers to that question provide two functions ( myformat.POSIXct and form ) that are supposed to solve this issue

The problem I am trying to solve is that I have a data frame with a sorted POSIXct variable in it. Each row is categorized and I want to get the time differences between each row for each level and add that data back into a new variable. The reproducible problem is as below. The below function is just for creating sample data with random times for the purpose of this question. random.time <- function(N, start, end) { st <- as.POSIXct(start) en <- as.POSIXct(end) dt <- as.numeric(difftime(en, st, unit="sec")) ev <- sort(runif(N, 0, dt)) rt <- st + ev return(rt) } The code for simulating the