How many columns and rows are you talking about? The easiest way is to copy each column and past it next to the orginal column. Then format the orginal column as a DATE and the copied column as TIME.
There is also the Text to column function (found under the Data menu). You can split columns this way. BUT, depending on how your date/time is formatted, it may/may not work. If your Date is obtained with the now function, it could be very difficult to do. Also using the Text to column function will probably show some unwanted numbers in the Date column and you will have to shorten the width of the column to hind those unwanted numbers (they would be something like 00 to show time).
IOW, it's not something that is all that easy to do and may take some thought and trial and error.