Global Days Calculator (Medicare Global Surgery Period)

How to use this calculator

1. Enter the procedure or surgery date as the date of service. Global periods are counted in calendar days from this date, including weekends and holidays.
2. Pick the global-period indicator (the GLOB DAYS value) for your CPT or HCPCS code from the Medicare Physician Fee Schedule Relative Value File: 000, 010, 090, or a special indicator MMM, XXX, YYY, or ZZZ.
3. If the indicator is YYY, also pick the 0, 10, or 90-day period your Medicare Administrative Contractor assigned, since YYY codes are contractor-priced.
4. Read the result: the pre-operative start (090 only), the post-operative window start and end dates, the total global days, and what is bundled into the surgical payment versus separately billable.
5. For MMM, XXX, ZZZ, or an unresolved YYY code, read the explanation of why no standard surgical window applies instead of a date.

How it works

Medicare bundles certain pre- and post-operative care into the single payment for a surgical procedure, and the length of that bundle is set by the code’s global-period indicator, the GLOB DAYS field in the Medicare Physician Fee Schedule. A global period is the span of related care that is already paid for by the surgery, so a follow-up visit inside it is generally not billed again. This calculator does the date math exactly the way CMS counts it (CMS MLN907166). You give it the surgery date and the indicator, and it returns the window.

For a 000 code, an endoscopy or other minor procedure, there is no pre-operative period and no post-operative follow-up days, so only the procedure day itself is global, a one-day period, and visits after that day are separately billable (CMS MLN907166). For a 010 code, other minor procedures, there is no pre-operative period and the global period totals 11 days: the surgery day plus the 10 days that follow, so the bundled post-operative window runs from the day after surgery through the tenth day after surgery (CMS MLN907166). For a 090 code, major surgery, CMS includes a one-day pre-operative period, the day before surgery, then the surgery day, then the 90 days that follow, for a total global period of 92 days; the bundled window runs from the day after surgery through the ninetieth day after surgery, and the tool also shows the pre-operative start date (CMS MLN907166). All of this is counted in plain calendar days, weekends and holidays included, with no business-day adjustment.

Four special indicators do not produce a standard surgical window, so the tool explains them rather than inventing dates. MMM marks maternity codes where the usual global concept does not apply. XXX marks codes the global concept does not apply to at all. ZZZ marks add-on codes that are billed with another service and carry no separate global period, so the period that matters is the primary code’s. YYY marks contractor-priced codes where your Medicare Administrative Contractor decides whether the period is 0, 10, or 90 days, so for YYY you can enter the period your MAC assigned and the tool will then compute the window (NGS Medicare).

During a 010 or 090 window, related post-operative evaluation-and-management follow-up visits are part of the surgical payment and not separately payable; CMS asks practitioners to report those visits with CPT code 99024 (Medicare Claims Processing Manual, Ch. 12). Services that are unrelated, or that meet the modifier criteria, can still be billed separately with the right modifier, such as 24 or 25 for E/M, 57 for the decision-to-operate visit, and 58, 78, or 79 for staged, return-to-OR, or unrelated procedures during the period. This tool tells you the dates and what they mean for billing; it does not decide separate billability for you.

Examples

If you enter June 2, 2025 with the 090 major-surgery indicator, the tool returns a 92-day total global period. The pre-operative day is June 1, 2025, the surgery day is June 2, 2025, and the post-operative window runs June 3, 2025 through August 31, 2025. The 90 in 090 names the follow-up days; CMS then adds the one pre-operative day and the surgery day to reach 92.

If you enter the same June 2, 2025 with the 010 minor-procedure indicator, the tool returns an 11-day total global period. There is no pre-operative period. The post-operative window runs June 3, 2025 through June 12, 2025, which is the surgery day plus the 10 days that follow.

If you enter June 2, 2025 with the 000 indicator, the tool returns a one-day global period: the procedure day, June 2, 2025, only. There is no pre-operative period and no post-operative follow-up window, so a visit after the procedure day is separately billable, which is the opposite of the 010 and 090 rule.

If you pick the ZZZ indicator, the tool computes no dates. ZZZ codes are add-on codes billed with another service and carry no separate global period, so there is no standard surgical window; the global period that applies is the one for the primary service the add-on is billed with.

What the data says

If you code surgical claims, the worry is familiar: does the window start the day of surgery or the day after, is it 90 days or 92, and will a routine post-op visit come back denied as included in the global. The numbers below show why getting that right matters.

Post-op visits rarely surface on the short windows and far more often on the long ones. A RAND analysis of 2019 Medicare claims found the observed-to-expected ratio of post-operative visits was only 0.04 for 10-day global procedures versus 0.38 for 90-day procedures, and 96.5 percent of 10-day procedures had no post-op visit reported at all (RAND Health Quarterly). That gap maps onto the 010 and 090 windows this tool computes, so knowing which window a code carries tells you a lot about whether to expect a bundled follow-up.

A calculator can show you the window, but whether a second procedure resets that window is its own question, and it turns on the modifier you append:

“Reporting modifier -58 will initiate a new global period for the CPT code reported. Modifier -78, on the other hand, does not prompt a new postoperative period, and the original global period remains.”

Joy Woodke, COE, OCS, OCSR, Director of Coding and Reimbursement, American Academy of Ophthalmology, in Retina Today.

The stakes are real money. A 2025 HHS Office of Inspector General audit found that 91 of 105 sampled global surgeries had fees that did not reflect the post-operative visits actually provided, which led OIG to estimate roughly 5.7 million dollars in net Medicare overpayments plus about 1.7 million dollars in extra cost-sharing paid by patients (HHS OIG, Report A-05-20-00021). Counting and bundling errors do not stay on the practice’s books; patients pay part of the difference.

A few mistakes come up again and again in coder discussions:

• People often start the count on the day of surgery, when the first bundled follow-up day is the day after, then argue over a window that ends a day early or late.
• People often assume their hand count is wrong when a 90-day global turns out to be 92 days once you add the pre-operative day and the surgery day.
• People often mix up which modifier applies, especially 24 versus 25 versus 57 on E/M visits and 58 versus 78 versus 79 on procedures.
• People often bill a routine post-op E/M that comes back denied as included in the global, unsure where routine follow-up ends and a separately billable complication or unrelated visit begins.
• People often assume a 000 code works like 010 and 090, when a 000 code has no post-op follow-up days, so visits after the procedure day are separately billable.

Global surgery indicators at a glance

These are the standard GLOB DAYS indicators you read off the Medicare Physician Fee Schedule, with what each one means for the window (CMS MLN907166). The calculator computes a window for 000, 010, and 090 (and for a YYY code once the MAC’s period is supplied); the rest get an explanation instead.

Indicator	Meaning	Post-op days counted	Pre-op day included?
000	Endoscopy or minor procedure	0 (day of surgery only)	No
010	Minor procedure	10	No
090	Major surgery	90	Yes (1 day before)
XXX	Global concept does not apply	n/a	n/a
YYY	Carrier or MAC determines the global period	Variable	Variable
ZZZ	Add-on code; global tied to the primary procedure	Same as primary	Same as primary
MMM	Maternity codes; usual global rules do not apply	n/a	n/a

What this tool does that others don’t

• It states the exact CMS day-counting convention on the page for every indicator: a 010 period is 11 total days (the surgery day plus 10 following), and a 090 period is 92 total days (one pre-operative day, the surgery day, and 90 following), per the CMS booklet (CMS MLN907166). Tools that show only a post-op end date never surface the 11 or 92 total.
• It outputs the one-day pre-operative period for 090 major procedures, the day before surgery that CMS includes in the 90-day package, so the total global days is the full 92 rather than an understated count that ignores the pre-op day.
• It handles the special indicators honestly. It detects MMM, XXX, YYY, and ZZZ and returns a plain explanation of why no standard window applies instead of forcing a misleading date, and it lets you resolve a YYY code to the 0, 10, or 90-day period your MAC assigned.
• It states, per case, what is bundled versus separately billable: related post-op E/M follow-up visits inside the window are bundled and reported with CPT 99024, while unrelated or qualifying services use modifier 24, 25, 57, 58, 78, or 79.
• Its primary path works from the indicator alone, not a CPT-code lookup, so the window is deterministic and reproducible and never returns a stale result because a code-to-indicator database drifted between fee schedule updates.

Limits of this estimate

This tool does the CMS calendar-day math for the indicator you pick. Keep these boundaries in mind before you rely on a window for a claim:

• It implements Medicare fee-for-service global-surgery rules only. Commercial payers, Medicaid, and Medicare Advantage plans may use different global windows, bundling, and modifier policies, so confirm the rule with the specific payer before relying on these dates for a non-Medicare claim.
• It cannot decide whether any specific service is separately billable. It shows the window and what is generally bundled, but separate billability turns on documentation and the correct modifier (24, 25, 57, 58, 78, 79), which is a coding judgment this tool does not make.
• It does not look up a CPT or HCPCS code’s global indicator for you. You must read the GLOB DAYS field from the current Medicare Physician Fee Schedule Relative Value File; entering the wrong indicator produces the wrong window.
• It does not compute a window for MMM, XXX, or ZZZ codes, because no standard surgical global period applies to them, and for YYY codes it can only compute a window after you supply the 0, 10, or 90-day period your MAC assigned.
• It computes one procedure’s window in isolation. It does not resolve overlapping global periods from multiple procedures, new global periods that start after a return to the operating room, or split global care between providers (modifiers 54, 55, 56).
• Global-surgery policy and the per-code indicators are set by CMS and can change with each annual fee schedule update. Re-check the indicator and the current CMS guidance for claims that span a policy year.
• The total global period counts more days than the indicator’s name: a 010 code is 11 total calendar days (the surgery day plus 10 following) and a 090 code is 92 total calendar days (1 pre-operative day, the surgery day, and 90 following days), per the CMS counting convention.
• The first bundled post-operative follow-up day is the day after surgery (S+1), because CMS counts the days following surgery. For a 000 code there are no post-operative follow-up days at all, so visits after the procedure day are separately billable.
• It counts windows in plain calendar days including weekends and holidays, with no business-day adjustment, using exact date arithmetic that accounts for leap days and month or year boundaries.

Frequently asked questions

Does the global period start the day of surgery or the day after?

For counting the bundled post-operative follow-up window, CMS counts the days following surgery, so the first bundled post-op day is the day after the procedure. But the total global period also counts the surgery day itself (and, for 090 major procedures, the day before surgery). That is why a 010 code is 11 total days, not 10, and a 090 code is 92 total days, not 90.

How many total days is a 90-day global surgery period?

92 calendar days. CMS counts one pre-operative day (the day before surgery), the surgery day, and the 90 days following surgery. So if surgery is on June 2, the pre-operative day is June 1, the procedure day is June 2, and the post-operative window runs June 3 through August 31.

How many total days is a 10-day global period?

11 calendar days. CMS counts the surgery day plus the 10 days following surgery. There is no pre-operative period for a 010 code. The bundled post-operative follow-up window runs from the day after surgery through the tenth day after surgery.

What does a 000-day global period mean?

It is a one-day period covering only the procedure day, used for endoscopies and some minor procedures. There is no pre-operative period and no post-operative follow-up days. A visit on the procedure day generally is not separately payable, but post-operative visits after the procedure day can be billed separately.

What do MMM, XXX, YYY, and ZZZ mean in global days?

They are special indicators where the standard global-surgery date math does not apply. MMM marks maternity codes billed under global obstetric package rules. XXX marks codes the global concept does not apply to. YYY marks contractor-priced codes, where your MAC sets the period at 0, 10, or 90 days. ZZZ marks add-on codes billed with another service that have no separate global period. This tool explains each rather than computing a misleading window.

Where do I find the global days for a CPT code?

Look up the code in the Medicare Physician Fee Schedule Relative Value File and read the GLOB DAYS field; it will show 000, 010, 090, or one of the special indicators. Enter that indicator here with your surgery date. This tool’s path works from the indicator, so you do not need a live code database to get the dates.

Are weekends and holidays counted in the global period?

Yes. Global periods are counted in plain calendar days, including weekends and holidays, with no business-day adjustment. A 90-day post-operative window simply runs 90 calendar days from the day after surgery.

Sources

• CMS Medicare Learning Network, Global Surgery booklet (MLN907166). The CMS day-counting convention for each indicator: 000 is the surgery day only, 010 is 11 total days, and 090 is 92 total days counting one pre-operative day, the surgery day, and the 90 days following. This CMS PDF is live but blocks direct automated fetch.
• Medicare Claims Processing Manual, Pub. 100-04, Chapter 12. The underlying manual sections (40 and 40.1) that define the global surgical package, the bundled post-operative care, and reporting bundled visits with CPT 99024. Live but blocks direct automated fetch.
• National Government Services, Global Surgery education page. A Medicare Administrative Contractor page that corroborates the indicator definitions, including YYY (contractor-priced) and ZZZ (add-on code).
• CMS Global Surgery Fact Sheet (ICN 907166), readable mirror via FindACode. A directly readable copy of the same CMS fact sheet confirming the 92-day, 11-day, and zero-day counting language.
• RAND Health Quarterly, post-operative visit analysis. The observed-to-expected post-op visit ratios of 0.04 for 10-day procedures and 0.38 for 90-day procedures, and that 96.5 percent of 10-day procedures had no post-op visit reported.
• HHS Office of Inspector General, Report A-05-20-00021. The 2025 audit finding 91 of 105 sampled global fees did not match the visits provided, with about 5.7 million dollars in net overpayments and 1.7 million dollars in patient cost-sharing.
• Retina Today, modifiers 58 and 78. Joy Woodke on how modifier 58 starts a new global period while modifier 78 leaves the original period running.