Medicare Enrollment Windows — Your Personal Dates
Your seven-month Medicare sign-up window is worked out from your birthday, and being born on the first of a month shifts the whole thing a month earlier. Enter your date of birth to estimate your own dates, see when coverage would start, and download them to your calendar. No email address required.
Works offline — your inputs never leave this device. How that works
Enter your date of birth
Your seven-month window runs from three months before the month you turn 65 to three months after it. Type your birthday on the left and this becomes real dates instead of a rule you have to apply to yourself.Every Medicare window, and what each one is for
Six windows, from Medicare's own pages. Two of them can create a lifetime penalty if they pass unused; the rest cost you options rather than money.
Initial Enrollment Period (Part A and Part B)
Missing this one can cost you
When
Seven months around your 65th birthday: it starts 3 months before the month you turn 65 and ends 3 months after that month. If your birthday falls on the 1st, the whole window shifts one month earlier — it starts 4 months before you turn 65 and ends 2 months after.
What it lets you do
Sign up for Part A and Part B for the first time. Sign up in one of the 3 months before your birthday month and coverage starts the first day of the month you turn 65; sign up during your birthday month or in the 3 months after, and coverage starts the following month.
General Enrollment Period (Part A and Part B)
Missing this one can cost you
When
January 1 through March 31 every year.
What it lets you do
Sign up for Part B (and premium Part A) if you missed your Initial Enrollment Period and do not qualify for a Special Enrollment Period. Since 2023 your coverage starts the month after you sign up — it no longer waits until July 1, which used to leave people uninsured for months. A late enrollment penalty usually still applies.
Special Enrollment Period after employer coverage ends
Missing this one can cost you
When
Starts the first month after your Initial Enrollment Period ends, and ends 8 months after the group health plan coverage or the employment ends, whichever happens first.
What it lets you do
Sign up for Part B (and premium Part A) with no late enrollment penalty, based on your own or your spouse's current employment. Two traps: COBRA is not group health plan coverage and does not extend this window, and retiree coverage does not qualify either. If you sign up while still working, or within the first full month after employer coverage ends, you can ask to delay your Part B start date up to 3 months.
Medicare Open Enrollment Period (Advantage and drug plans)
No penalty for missing it
When
October 15 through December 7 every year.
What it lets you do
Join, drop or switch a Medicare Advantage plan (with or without drug coverage), switch between Original Medicare and Medicare Advantage, or join, drop or switch a Medicare drug plan. Coverage starts January 1 of the next year, and the plan must get your request by December 7.
Medicare Advantage Open Enrollment Period
No penalty for missing it
When
January 1 through March 31, and only if you are already enrolled in a Medicare Advantage plan.
What it lets you do
Switch to a different Medicare Advantage plan (with or without drug coverage), or drop your Advantage plan and go back to Original Medicare — in which case you can also join a separate Medicare drug plan. Coverage starts the first of the month after the plan gets your request. This window does not let you join an Advantage plan from Original Medicare.
Medigap Open Enrollment Period
No penalty for missing it
When
Six months, starting the first month you have Medicare Part B and are 65 or older. It is one-time only — it does not repeat each year.
What it lets you do
Buy any Medigap policy sold in your state at the best available price, with no medical underwriting: the insurance company cannot refuse you or charge you more because of pre-existing health problems. After this window closes you may not be able to buy a Medigap policy at all, or it may cost more. Missing it does not create a Medicare late enrollment penalty, but it can permanently change what supplemental coverage you can buy.
If a window has already passed
The late enrollment penalty calculator estimates what a delay adds to a premium, and shows the Part B rule that only counts full twelve-month periods. Employer coverage often means no penalty at all.Where to take a plan question
We take no money from any insurer and name none, so we are not the place to settle what you buy. These three are, and all of them are free.
Verified 2026-08-02 against Medicare.gov, "When does Medicare coverage start?" (Initial, General and Special Enrollment Periods); plan windows from Medicare.gov, "Joining a plan" (https://www.medicare.gov/basics/get-started-with-medicare/get-more-coverage/joining-a-plan); Medigap window from Medicare.gov, "Medigap basics" (https://www.medicare.gov/health-drug-plans/medigap/basics) (effective 2026-01-01)
Estimate only — not financial, tax, legal, or insurance advice. Only MEDICARE can determine your actual amounts.
Official source: Medicare.gov — When does Medicare coverage start? ↗
🎓 Understand this tool
What it is
Your own Medicare dates, worked out from your date of birth: when the seven-month sign-up window opens and closes, the date after which coverage starts late, the January-to-March window for anyone who missed it, and the one-time Medigap window measured from your Part B start date.
How it works
The Initial Enrollment Period runs three months before the month you turn 65, that month, and three months after. Social Security treats a person as attaining an age the day before their birthday, so anyone born on the 1st of a month attains 65 in the previous month and the whole window moves a month earlier. Coverage begins on the first of your birthday month if you signed up in the earlier three months, and the month after you enroll otherwise.
Getting the most from it
- Enter your date of birth. It stays in your browser — nothing about this calculation is sent anywhere, which is why no email address is asked for at any point.
- If you are already enrolled in Part B, add the date it started. That is what dates your six-month Medigap window, and it is the one window that never comes back.
- Download the calendar file. It writes all-day reminders with no alarms into your own calendar, so the dates survive long after you have closed this page.
- Read the window list underneath for the fall window and the Special Enrollment Period that follows employer coverage — those are the ones that apply after 65 rather than at it.
Reading your result
The dates are an estimate produced by applying the published rules to the birthday you entered. The two that matter most are the sign-up-by date, after which your coverage start slips by a month, and the closing date of the window, after which a lifelong Part B penalty can begin to accrue unless you qualify for a Special Enrollment Period.
What it can't tell you
It cannot know whether you have employer coverage that changes the picture, whether you are already enrolled automatically because you draw Social Security, or whether a disability or a diagnosis moved your eligibility earlier than 65. Social Security holds the record of your actual dates, and their record is the one that governs.
Frequently asked questions
It runs seven months: the three months before the month you turn 65, that month, and the three months after. Enter your date of birth above and this tool prints those dates as real dates rather than as a rule you have to apply to yourself, then estimates when coverage would actually begin.
Related calculators
Late Penalty Calculator
Sign up for Medicare Part B or Part D late and the surcharge is permanent. Enter how many months you went without each kind of coverage to estimate what the penalty adds every month, every year, and over a horizon you choose. Part B counts full twelve-month periods only, so partial years cost nothing.
Medigap vs Advantage
Medigap and Medicare Advantage do not cost more or less than each other — they put the cost in different places. One front-loads predictable premiums, the other front-loads less and exposes you to out-of-pocket charges up to a yearly maximum. Here is the structure of each, in figures CMS publishes, with no plan named.
Part B Premium
The standard Medicare Part B premium and annual deductible for 2026, taken straight from the CMS notice that set them, with every year back to 2016 so you can see how fast this line item has actually risen. Higher earners pay more through IRMAA; this page shows the base figure everyone starts from.
Annual update alerts — new tax and benefit figures the week they drop
One email when the numbers change. Double opt-in, no spam, unsubscribe anytime.