How to parse milliseconds?
Courtesy of the ?strptime help file (with the example changed to your value):
z <- strptime("2010-01-15 13:55:23.975", "%Y-%m-%d %H:%M:%OS")
z # prints without fractional seconds
op <- options(digits.secs=3)
z
options(op) #reset options
You can also use strptime(time[1], "%OSn") where 0 <= n <= 6, without having to set digits.secs.
The documentation states "Which of these are supported is OS-dependent." so YMMV.