[R] Strange result for strptime with %p

[Marc Girondot]

Dear members... are these results normal ?

For the first one, no problem. I expected this:

 > strptime("05/01/18 01:00:00 AM", format = ("%m/%d/%y %I:%M:%S %p"), 
tz="Asia/Jayapura")
[1] "2018-05-01 01:00:00 WIT"

For this one, it is ok also:

 > strptime("05/01/18 01:00:00 AM", format = ("%m/%d/%y %I:%M:%S %p"), 
tz="Asia/Jayapura")-1
[1] "2018-05-01 00:59:59 WIT"

But how to explain this ???

 > strptime("05/01/18 00:59:59 AM", format = ("%m/%d/%y %I:%M:%S %p"), 
tz="Asia/Jayapura")
[1] NA

Thanks for your advices
Marc
______________________

R 3.5.1 on MacOS 10.14

 > version
                _
platform       x86_64-apple-darwin15.6.0
arch           x86_64
os             darwin15.6.0
system         x86_64, darwin15.6.0
status
major          3
minor          5.1
year           2018
month          07
day            02
svn rev        74947
language       R
version.string R version 3.5.1 (2018-07-02)
nickname       Feather Spray