The touch command in UNIX creates a file if it does not exist or updates the modification time of an existing file to the current time. An option of the touch command allows the modification timestamp to be set to any arbitrary time.
To change the modification time (the time displayed in a long listing of the file) of a file called testfile to November 18, 2000, 2:30 PM, use the following command:
touch -t 200011181430
This will alter the modification time of an existing testfile or, if not present, will create an empty file with that timestamp.
The format of the timestamp is as follows:
Date and time elements in square brackets are optional. Thus, the minimum timestamp includes month, day, hour, and minute.