Short answer: it depends on the country and the context.

• United States: The federal fiscal year runs from October 1 to September 30 (one 12-month period). Some states, cities, and companies choose different fiscal years.
• United Kingdom: The tax year (also called the financial year) runs from April 6 to April 5 of the next year.
• India: The financial year typically runs from April 1 to March 31.
• Other countries vary; many use calendar year (January 1 to December 31) for accounting, while others use a different fiscal year aligned to their business cycle.

If you can specify the country or the organization (e.g., your company, government entity, or a specific jurisdiction), I can give you the exact dates for that case.