If the file do not exist, this property returns
nil
and setting its value will have no effect.File.modified read/write property
The File.modified property set or get a Datetime value indicating when the file has been last modified. The file must exist physically on the disk.
Example
local file = sys.File("newfile.txt"):open("write")
file:write("This is a test file")
file:close()
local timestamp = sys.Datetime("01/01/1970")
file.modified = timestamp
-- outputs "true"
print(file.modified.date == timestamp.date)