While there I inquired about their discounts. I found out that they offer a 10% Military Discount. This of course varies from location to location but the 4 locations I have been to have all offered that discount. So i'm pretty sure you won't have any problems with Denny's honoring the discount. From their Veterans Day press release last year they stated:
"Select Denny’s nationwide offer a 10 percent military discount year-round for diners with proof of service. For more information or to find a participating Denny’s near you, please visit www.dennys.com."
Don't forget that Denny's always celebrates Veterans/Military with "All You Can Eat Pancakes" on Veterans Day. Last year on Nov 11, 2013 they offered never ending stacks of their famous buttermilk pancakes to active, inactive and retired military personnel. To read the press release from last year click here
Denny's also has a 55+ menu that has great deals for old fogies.
Denny's actually has a better discount for AARP members which is 15% off. This was odd because in my experience restaurants usually give their highest discount to military members but here is an exception.
If you are not an AARP member, you can join for just $16 a year (or $12 for a five year subscription). That comes with a free subscription for your spouse also. They have discounts to Movies, Car Rentals, Hotels, Restaurants, etc.