A company's fiscal year is the twelve-month period its annual report covers. Many companies use the calendar year, but many do not: retailers often end their year after the holiday season, and some technology companies end theirs in June or September.
Names can mislead
Companies usually name a fiscal year after the calendar year in which it ends, but not always. A "fiscal 2027" can be mostly in calendar 2026. Read the dates, not the label.
52 and 53 week years
Some companies end their year on the same weekday each year, such as the last Saturday of January, rather than on a fixed date. Their years run 52 weeks, with a 53rd week every five or six years. A 53 week year has an extra week of sales, which flatters growth that year.
On Listed
Each company page shows its fiscal year end. In the SEC's company facts data, the fiscal year label attached to a figure describes the filing it came from, not the period the figure covers, so a 10-K's prior-year comparison figures carry the new year's label. Listed places each figure by its own start and end dates instead.