Well, without knowing the specific 'every dog has its day short story', generally it might be about a character or an entity who finally gets a chance to shine or succeed after a period of being overlooked. For example, a person who has been in the shadows at work but then gets an opportunity to prove themselves and has their'moment' of glory.
I'm not sure about the exact story. But usually in a story with this title, it could center around an underdog. Maybe it's a small, unassuming dog in a story full of big, fancy dogs. And one day, this little dog does something amazing, like saving the day in the neighborhood or winning a local dog competition against all odds. That's how the idea of 'every dog has its day' would play out in a short story.
Since I don't have the actual text of the 'every dog has its day short story', I can only guess. It might tell the story of a dog that is always teased or ignored. However, through a series of events, like befriending a helpful animal or finding a hidden talent within itself, it has a day where it is the center of attention and is praised. It could also be a metaphor for a human in a similar situation, where they break free from their ordinary or difficult circumstances for a brief, glorious moment.