# test date-time object
options(digits.secs = 3)
d = as.POSIXct("2016-08-30 14:18:30.58", tz = "UTC")
format(d,"%S") # 00-61 Second as integer
## [1] "30"
format(d,"%OS") # 00-60.99… Second as fractional
## [1] "30.579"
for...