If you want to specifically convert "2007-02-01 00:00:00" to a date-class object, this is what you need to do. This is based on this question and answer
print.POSIXct <- function(x,...)print(format(x,"%Y-%m-%d %H:%M:%S"))
x <- "2007-02-01 00:00:00"
x <- as.POSIXct(x,tz=Sys.timezone())
x