If you are military, Delta is plenty happy with the AFORMS printout or the equivalent from other services. I had a small electronic logbook with printout for my civilian time and the massive paper copy of my military time.

But this question makes me wonder what world you're living in. Who thinks it's ok to go to a major airline interview without proof of time? If you really think this you probably are a bit rusty in other areas as well, I highly recommend ECC or a similar service for your interview prep since you didn't do very well on this question and it's a gimme.