Is R superstitious regarding POSIXct data type

Question

For a project, I was converting strings to POSIXct format using strptime function.

x <- strptime("2016-03-13 02:56:16", "%Y-%m-%d %H:%M:%S")
class(x)
[1] "POSIXlt" "POSIXt" 
x + 3600
[1] NA

Although class(x) results in "POSIXlt" "POSIXt", doing x + 3600, I get NA

If I do a similar procedure for 2017 with the same month, day, hour, minute, second, it works!

x <- strptime("2017-03-13 02:56:16", "%Y-%m-%d %H:%M:%S")
class(x)
[1] "POSIXlt" "POSIXt" 
x + 3600
[1] "2017-03-13 03:56:16 EDT"

Looking back at my data, I see a list of dates where there will be a problem in date conversion!

[1] "2016-03-13 02:51:02" "2016-03-13 02:49:46" "2016-03-13 02:24:15" "2016-03-13 02:37:52" "2016-03-13 02:56:16"
[6] "2016-03-13 02:59:32" "2016-03-13 02:49:29" "2016-03-13 02:27:20" "2016-03-13 02:22:20" "2016-03-13 02:44:11"
[11] "2016-03-13 02:43:31" "2016-03-13 02:44:46" "2016-03-13 02:07:48" "2016-03-13 02:36:36" "2016-03-13 02:51:39"
[16] "2016-03-13 02:00:13" "2016-03-13 02:42:37" "2016-03-13 02:48:53" "2016-03-13 02:53:05" "2016-03-13 02:01:41"
[21] "2016-03-13 02:57:36" "2016-03-13 02:40:09" "2016-03-13 02:27:19" "2016-03-13 02:33:08" "2016-03-13 02:18:51"
[26] "2016-03-13 02:05:45" "2016-03-13 02:06:09" "2016-03-13 02:06:09" "2016-03-13 02:03:25" "2016-03-13 02:32:14"
[31] "2016-03-13 02:59:34" "2016-03-13 02:35:39" "2016-03-13 02:51:10" "2016-03-13 02:50:56" "2016-03-13 02:38:56"
[36] "2016-03-13 02:25:35" "2016-03-13 02:20:09" "2016-03-13 02:30:43" "2016-03-13 02:00:04" "2016-03-13 02:51:55"
[41] "2016-03-13 02:26:25" "2016-03-13 02:37:20" "2016-03-13 02:49:29" "2016-03-13 02:35:50" "2016-03-13 02:05:38"
[46] "2016-03-13 02:15:10" "2016-03-13 02:54:23"

If I change the year to 2015 or 2017, or change the day from 13 to something else, it works. It seems that there is something going on March 13th of 2016. Am I missing something or this is a flaw within R?

I am using R version 3.3.2 (2016-10-31)

Answer 1

The problem is that there was no such time as "2016-03-13 02:56:16". 13 Mar 2016 was when Daylight Savings Time started. At 2AM, that day, the clock jumped immediately to 3AM.