format time using as.POSIX in R

format time using as.POSIX in R

I want to put time month-date-year hour-min into my time series data
called test. I want to specify the starting time as 01-01-2014 00:00:00.
My code returns error and I tried several times but still cannot fix it.
> t<-c("01-01-2014 00:00:00")
> solar_inp<-xts(test, seq(from=as.POSIXct(test,origin=t),
length.out=8760,by=as.difftime(1,units='hours')))
Thank you very much!