Which choice returns [1] "2019-09-28"?
format(as.POSIXct("Sep-28-2019 07:54:31 AM",format='%b%d%Y'))
as.POSIXlt("Sep-28-2019 07:54:31 AM",format='%b-%d-%Y')
as.POSIXct("Sep-28-2019 07:54:31 AM UTC")
format(as.POSIXct("Sep-28-2019 07:54:31 AM UTC",format='%b-%d-%Y'))