日期和时间在单独的列中，转换为R中的日期时间

I am importing some data from NOAA and it has dates and times in separate columns. I searched for an elegant way to append a single datetime column in my R dataframe but was unable. I found a stack exchange question about the inverse but not this one. Is there a simple as.Date command I could run? I am simply using read.table for a downloaded text file and it imports just find.I am importing some data from NOAA and it has d