NA when adding 60 seconds to date times with 59 minutes

[garrettgman]

Adding seconds returns NAs when result has new hour and zero seconds

library(lubridate)
ymd_hms("2015-01-01 00:59:00") + seconds(60)
## [1] NA
ymd_hms("2015-01-01 01:59:00") + seconds(60)
## [1] NA
ymd_hms("2015-01-01 23:59:00") + seconds(60)
## [1] NA
ymd_hms("2015-01-01 00:59:05") + seconds(55)
## [1] NA
ymd_hms("2015-01-01 00:59:59") + seconds(1)
## [1] NA

Doing the equivalent with minutes(1) works

ymd_hms("2015-01-01 00:59:00") + minutes(1)
## [1] "2015-01-01 01:00:00 UTC"
ymd_hms("2015-01-01 01:59:00") + minutes(1)
## [1] "2015-01-01 02:00:00 UTC"
ymd_hms("2015-01-01 23:59:00") + minutes(1)
## [1] "2015-01-02 UTC"

NA only occurs when result has new hour and zero seconds

ymd_hms("2015-01-01 00:59:00") + seconds(59)
## [1] "2015-01-01 00:59:59 UTC"
ymd_hms("2015-01-01 00:59:00") + seconds(61)
## [1] "2015-01-01 01:00:01 UTC"
ymd_hms("2015-01-01 00:58:00") + seconds(60)
## [1] "2015-01-01 00:59:00 UTC" 

NA does not occur when adding more than 60 seconds to create new hour and zero seconds

ymd_hms("2015-01-01 00:58:59") + seconds(61)
## [1] "2015-01-01 01:00:00 UTC"
ymd_hms("2015-01-01 00:58:55") + seconds(65)
## [1] "2015-01-01 01:00:00 UTC"
ymd_hms("2015-01-01 23:58:00") + seconds(120)
## [1] "2015-01-02 UTC"

[stevencb]

This bug is probably related to what was reported in issue #217.