Definition
This idiom is used to convey that everyone will experience a period of success or good fortune at some point in their lives.
He has had bad luck for the past few years, but he believes that every dog has its day.
Although she is facing many challenges now, she knows that every dog has its day, and her opportunity will come.
The team hasn't performed well this year, but they still hope that every dog has its day and look forward to winning a championship in the future.