We speak about both financial and accounting year. This is the closing date of the accounting (purchases, sales, fees, taxes, etc.). With madeinlaw.com, you choose the closing date of your first financial year, and the following years will end on that same date each year.
Please note that the end of the first financial year must be fixed not more than 23 months after the date of the first financial year and only including up to two calendar years!
In practice, companies generally choose a date 18 months after the company's incorporation and generally in September or October to avoid the December 31 rush and tax processing delays.