Fear After the 4th of July

Question: Tracy, my dog doesn't want to go outside for walks after dark since the 4th of July. How can I help him get over his fear?

I would stop the walks immediately.   He IS scared/anxious, and repeated exposure doesn't make the fear/anxiety decrease, it merely adds other negative things to his level of anxiety (i.e. you having to go get him, him giving you submissive body language asking you to 'please leave me alone and don't hurt me).  A great many dogs do just great with NO walks at all.  They get plenty of exercise in the yard. 
 
How to rebuild the dog's confidence for walks/going outside at night:
 
What you can do to help him through this is to just leave him alone for 1-2 weeks.  When the weather is cooler, take him for a walk at least 1 hour before it gets dark.  Provide lots of treats and happy talk.   Arrive home at least 15 minutes before it gets dark. 
 
If he does well, and show no signs of anxiousness, then the next week, start the walk 45 minutes before dark time.  Lots of treats and happy talk.  Arrive home just before it gets dark.  If he will eat treats in the security of the front yard, feed him treats and ask for sits or TOUCH (no DOWNS!) on the front porch as it gets darker.  If he quits eating or seems stressed, TAKE HIM INSIDE.   
 
He will let you know when he is ready to move to the next step (30 minutes before dark, 15 minutes before dark, etc.)  If he is calm and relaxed and not anxious or fearful, continue exposing him to the later hour/darkness.  If he is still upset, you need to back up a few steps until he is feeling confident again.
 
This is not something you cannot force him through. He is not doing this to be willful or, to be stubborn.  Think of his fear like your or a friend's fear of spiders, snakes or heights, etc.  It has nothing to do with you, or with your relationship with your dog.  But he needs your support and help to work through it successfully.