We have a field that we track paperwork with that is 9 characters. The first 4 characters are a 'julian date', the 5th character is a dash and the last 4 characters are sequential.
example:
For today, we would use 4085-0001, 4085-0002, 4085-0003, etc.
For yesterday: 4084-0001, 4084-0002, etc...