In insurance, a calendar year refers to the standard January 1 to December 31 period used as the benefit period for some health plans. When a plan uses a calendar-year benefit period, all deductibles, annual maximums, and benefit limits reset on January 1 each year. This contrasts with an anniversary-year benefit period, which resets on the anniversary of your policy's effective date. Knowing whether your plan uses a calendar year or anniversary year is important for planning treatments — for example, scheduling a dental crown in December and the follow-up in January could allow you to use two years' worth of dental maximums. Calendar-year plans are common in group benefits. Individual plans may use either calendar year or anniversary year depending on the insurer.