How to convert time stamp string “2014-07-20T05:11:49.988Z” into POSIXt in R?

Question

How to convert time stamp string “2014-07-20T05:11:49.988Z” into POSIXt in R?

I want to know why the second is represented in 3 decimel places? also what is the mean

Answer 1

The lubridate package has very robust parsers that I tend to prefer over manual specification of the format in base R

library(lubridate)
#> 
#> Attaching package: 'lubridate'
#> The following object is masked from 'package:base':
#> 
#>     date

(t <- ymd_hms("2014-07-20T05:11:49.998Z"))
#> [1] "2014-07-20 05:11:49 UTC"

^{Created on 2019-03-11 by the reprex package (v0.2.1)}

Making sure that the milliseconds that aren't printed aren't lost either:

second(t)
#> [1] 49.998

Answer 2

The "Z" is shorthand for UTC. You can parse this in base R with

x <- as.POSIXct("2014-07-20T05:11:49.998Z", 
    format="%Y-%m-%dT%H:%M:%OSZ", tz="GMT")

Note that you generally either use POSIXct or POSIXlt rather than POSIXt directly (both have POSIXt as a base class)