No, six months is not 180 days. Any six consecutive calendar months add up to between 181 and 184 days, so “six months” is always longer than “180 days” by one to four days. The gap sounds trivial until it costs you a filing window, a tax benefit, or a warranty claim, because courts, agencies, and contracts treat the two measurements as different things.
The Actual Day Counts
Calendar months run 28 to 31 days, so no six-month block ever lands on exactly 180. The shortest stretch is January through June in a non-leap year: 31 + 28 + 31 + 30 + 31 + 30 = 181 days. The longest is any six-month run containing both July and August, each with 31 days. March through August, for example, totals 184. In a leap year, February’s extra day pushes the January-through-June minimum to 182.
The second half of a common year (July through December) runs 184 days. The first half runs 181. Even when February sits inside the window, the longer months around it more than make up the difference. So a contract or statute that says “180 days” is always a shorter deadline than one that says “six months,” even though people use the phrases interchangeably in conversation.
How Courts Read “Months” Versus “Days”
When a statute or contract uses “months” without a day count, courts apply the calendar-month rule. One month from March 15 ends on April 15, whether March has 30 or 31 days. Six months from March 15 ends on September 15. The count follows the calendar grid, which gives parties a predictable framework for leases, notice periods, and filing windows.
If the ending month has no matching date, the deadline falls on the last day of that month. One month from January 31 ends on February 28, or February 29 in a leap year. Careful drafters who need an exact day count write “180 days” or “183 days” instead of “six months” to avoid the ambiguity.
When a deadline is written in days, courts count sequentially. Under Federal Rule of Civil Procedure 6, the day of the triggering event is excluded, every calendar day after that counts (weekends and holidays included), and the last day is included. If the last day lands on a Saturday, Sunday, or legal holiday, the deadline rolls to the next business day.1Legal Information Institute. Federal Rules of Civil Procedure Rule 6 – Computing and Extending Time The EEOC uses the same approach: weekends and holidays count toward the total, but if the final day falls on one, you get until the next business day.2U.S. Equal Employment Opportunity Commission. Time Limits For Filing A Charge
EEOC Discrimination Charges: Where One Day Matters
Federal employment discrimination law gives you 180 calendar days from the date of the discriminatory act to file a charge with the Equal Employment Opportunity Commission.2U.S. Equal Employment Opportunity Commission. Time Limits For Filing A Charge Miss that window and the EEOC will almost certainly reject the charge, which in most cases permanently bars the claim in court.
This is exactly where confusing six months with 180 days gets dangerous. If the discriminatory act happened on January 15, six calendar months forward is July 15. But 180 days from January 15 is July 14. File on July 15 thinking you had about six months, and you are a day late. The deadline stretches to 300 calendar days when a state or local agency enforces its own anti-discrimination law covering the same conduct, so many workers effectively have the longer window, but you should confirm your state’s coverage before relying on it.2U.S. Equal Employment Opportunity Commission. Time Limits For Filing A Charge
1031 Exchanges: 180 Days, Not Six Months
Investors doing a like-kind exchange under Section 1031 face two deadlines, both counted in days. You have 45 days from the sale of the relinquished property to identify replacement properties in writing. You then have 180 days from that same sale date to close on the replacement, or the due date of your tax return for the year of the sale (with extensions), whichever comes first.3Office of the Law Revision Counsel. 26 USC 1031 – Exchange of Real Property Held for Productive Use or Investment
Neither deadline can be extended short of a presidentially declared disaster. Treating 180 days as “roughly six months” and scheduling a closing near the end of that rough estimate is a common way to blow a 1031 exchange. Miss the day by one, and the entire capital gain becomes taxable. Count forward from the sale date on a calendar and work back from the hard number.
Where Day Counts and Month Counts Are Not Interchangeable
The IRS substantial presence test uses a 183-day threshold to decide whether a foreign national is a U.S. tax resident, and the calculation runs across three years. You must be present in the U.S. for at least 31 days in the current year, and your weighted total must reach 183: all days in the current year, one-third of days in the prior year, and one-sixth of days from two years back.4Internal Revenue Service. Substantial Presence Test Someone physically present for roughly six months (about 182 days) in the current year could meet the threshold once prior-year fractions are added, or could fall short with little recent U.S. presence. The test counts individual days and applies a formula; calendar months do not enter into it.
Social Security disability goes the other direction. The five-month waiting period before benefits begin is measured in full calendar months, not days.5Social Security Administration. Approval Process – Disability Benefits If your disability onset date is March 10, the five full months run April through August, and the first payment covers September. Partial months do not count, so an onset of March 1 and an onset of March 31 produce the same first payment date. In a day-counted rule every day moves the deadline. In a month-counted rule, days within the starting month often do not.
Passports and Private Contracts
Many countries deny entry if your passport expires within six months of arrival, and airlines sometimes enforce the rule at the gate. Because the rule is measured in calendar months, actual required validity ranges from 181 to 184 days depending on when you travel. If your passport expires fewer than 185 days from your departure date, check the specific entry requirements for your destination before you book. “About six months” is not precise enough when a border agent is deciding.
Private contracts use both formats, and the choice is not cosmetic. A 180-day warranty runs exactly 180 days from the triggering event. A six-month warranty runs to the same calendar date six months later. When a product fails right at the boundary, those one to four extra days determine whether the manufacturer owes you a repair. Certificates of deposit, post-IPO lock-ups, and insurance claim windows typically use day counts (often 90 or 180) to remove the ambiguity. When you sign anything with a time limit, read whether the deadline is in days or months and count accordingly. Assume 180 days when the contract says six months and you may act too early. Assume six months when it says 180 days and you may act too late.
How to Count Without Getting Burned
Do not convert between days and months in your head. If a deadline says 180 days, open a calendar and count 180 days from the triggering event, excluding the event day itself, consistent with how federal courts compute time. If it says six months, find the same calendar date six months later, applying the last-day-of-month rule when needed. Mark both dates on the calendar and build in a few days of personal margin before each.
Check whether the governing rules allow a next-business-day extension when the deadline falls on a weekend or federal holiday. Federal court filings and EEOC charges do.1Legal Information Institute. Federal Rules of Civil Procedure Rule 6 – Computing and Extending Time Many private contracts and some administrative deadlines do not. The safest assumption is that the deadline on the page is the deadline, unless a specific rule says otherwise.