First, a quick definition of what year-over-year means. Year-over-year compares results from one time period to the same time period in the previous year.
When a company reports its quarterly financial results, it will typically at least announce its revenue and earnings-per-share for the preceding three-month period.
Aside from the quarterly financial statements, companies typically also discuss their results in a press release and a conference call with analysts who cover the stock.
Think of retailers such as department stores, which generate the vast majority of their annual profits in the fourth quarter, during the busy holiday shopping season.