使用 as.POSIXct 将日期从“字符”格式转换为“POSIXct”时，1 个特定日期的 NA

Question

I'm converting a string vector to date format with as.POSIXct(). Here is the strange thing:

as.POSIXct("2017-03-26 03:00:00.000",format="%Y-%m-%d %H")

#Gives

"2017-03-26 03:00:00 CEST"

#While

as.POSIXct("2017-03-26 02:00:00.000",format="%Y-%m-%d %H")

#Outputs
NA

This is really confusing and frustrating. It seem like the function really doesn't like the specific time: 02:00:00.000

Answer 1

We can specify the %T for time. In the format, there are minutes, seconds and millseconds. So, the %H is only matching the hour part

as.POSIXct("2017-03-26 02:00:00.000",format="%Y-%m-%d %T")
[1] "2017-03-26 02:00:00 EDT"

Or to take care of the milliseconds as well

as.POSIXct("2017-03-26 02:00:00.000",format="%Y-%m-%d %H:%M:%OS")
#[1] "2017-03-26 02:00:00 EDT"

---

Or using lubridate

library(lubridate)
ymd_hms("2017-03-26 02:00:00.000")

Answer 2

This was a daylight savings issue, the time:

"2017-03-26 02:00:00.000" does not exist in Sweden as we lost an hour this date when changing to "summer time".