Convert date time to a formatted time string

Not sure why we need to convert to hms and back to initial string format. Maybe parse_date_time function is what you need:

library(lubridate)

myTime <- "14:11:49"
hms(myTime)
#"14H 11M 49S"

POSIXct_myTime <- parse_date_time(myTime,"hms")
format(POSIXct_myTime, format="%H:%M:%S")
#"14:11:49"

---

EDIT: We can use paste:

tt <- hms("14:11:49")
tt
#[1] "14H 11M 49S"
tt <- tt + minutes(3)
tt
#[1] "14H 14M 49S"

paste(hour(tt), minute(tt), second(tt), sep = ":")
#[1] "14:14:49"

Benchmark output:

big <- rep(tt, 10000)
bench::mark(
  paste = paste(hour(big), minute(big), second(big), sep = ":"),
  sprintf = sprintf("%s:%s:%s", hour(big), minute(big), second(big)),
  shosaco = format(Sys.Date() + big, "%H:%M:%S"))
# # A tibble: 3 x 13
#   expression    min median `itr/sec` mem_alloc `gc/sec` n_itr  n_gc total_time
#   <bch:expr> <bch:> <bch:>     <dbl> <bch:byt>    <dbl> <int> <dbl>   <bch:tm>
# 1 paste      27.7ms 29.8ms      30.9  312.69KB        0    16     0      517ms
# 2 sprintf    29.5ms 42.7ms      23.3  312.69KB        0    12     0      515ms
# 3 shosaco    28.3ms 29.2ms      33.1    2.06MB        0    17     0      514ms
# # ... with 4 more variables: result <list>, memory <list>, time <list>,
# #   gc <list>

The proposed solution does not print leading zeros. The following solution seems to be more elegant:

> t <- hms("14:01:49") + minutes(3)
> sprintf("%s:%s:%s", hour(t), minute(t), second(t))
[1] "14:4:49" # looking weird
> format(Sys.Date() + t, "%H:%M:%S")
[1] "14:04:49" # looking better

The problem is that class(t) is "Period" and the format.Period() function does not have a parameter for format=. The t object is not a standard POSIXt style object that you may be used to using with format(). Only the format.POSIXct() and format.POSIXlt() functions will behave like that.

So perhaps the easiest thing to do would be to define a helper function to turn the Period class into POSIXct. We can do that with:

as.POSIXct.Period <- function(x, start=today()) {
    X<-as.interval(x, start); 
    [email protected]+X@start
}

It's important to note that POSIXct is a date/time value, not just a time value. So by default we just assume it started at midnight today. But then we can use format in the way you wanted

format(as.POSIXct(t), format="%H:%M:%S")
# [1] "14:11:49"

I must admit I'm not an expert lubridate user so perhaps I've overlooked an obvious function, but it seems the options for formatting lubridate classes into "pretty" formats are very limited.