180 Days From a Date Calculator

What this 180 day calculator does with your date

Most 180 day pages answer one question about today. This one takes the date you give it. Type a closing date, a lease start, a surgery date or a purchase date, and it returns the day 180 days after it, the day 180 days before it, and the weekday each one lands on, so you can see at a glance whether a deadline eats a Saturday.

The count uses the day zero convention: the date you type is day 0, and the next morning is day 1. From November 4, 2026 the forward answer is Monday, May 3, 2027 and the backward answer is Friday, May 8, 2026. Neither is 179 or 181 days away, which is the error a hand count makes when it forgets whether to include the first day.

The mode menu changes what a day means. Calendar days count every square on the wall calendar. Business days count Monday through Friday only, so 180 of them stretch across 252 calendar days. The third setting also skips the eleven US federal holidays, which pushes the landing date about two weeks further out.

One promise worth stating: the arithmetic runs in your browser. Nothing you type is uploaded, logged or stored.

Two starts, counted month by month

Hand counting works if you keep a running total and stop at 180. Start with November 4, 2026. November has 30 days, so the first leg carries 26 of them, from the 4th through the 30th. December adds 31 for a running total of 57, then January 31 (88), February 28 (116), March 31 (147) and April 30 (177). Three days remain, which puts the answer at Monday, May 3, 2027.

The same walk from August 31, 2026 shows where counts go wrong. September carries 30 (30), October 31 (61), November 30 (91), December 31 (122), January 31 (153) and February 28 (181). That overshoots by one, so the last leg stops a day early, at Saturday, February 27, 2027. Add whole months until one more would break the total, then take only the days you still need.

A second opinion takes one step: 25 weeks lands on the start weekday, and the leftover 5 days move it five places forward. November 4, 2026 is a Wednesday, and Wednesday plus five is Monday. Running both methods is the fastest way to catch a dropped month.

Month ends, leap days and the rollover trap

Two kinds of date math look alike and are not. Adding 180 days needs only a day count, so August 31, 2026 plus 180 is February 27, 2027. Adding six months needs a rule for a day number the target month may not have, and that rule is where software quietly produces a wrong date.

In JavaScript, new Date(2027, 1, 29) does not fail. February 2027 has 28 days, so the engine rolls the value forward and returns March 1, 2027. Add six months to August 31, 2026 the same careless way and you get March 3, 2027, three days past the date most leases intend, which is February 28, 2027.

The correction is to clamp: keep the year and month, then cap the day at the last day of that month. The calculator here clamps, so its six month row shows February 28.

Leap day is the other edge. February 29, 2028 exists, and 180 days after it is Sunday, August 27, 2028. February 29, 2027 does not exist, so a typed 2027-02-29 is rejected and the page falls back to today instead of inventing March 1.

180 calendar days or 180 business days

Business day counts ignore Saturday and Sunday, so the same 180 lands much later. The quick estimate is 180 divided by 5, times 7, which gives 252 calendar days, and for a start that misses a holiday cluster the estimate is exact: 180 business days after November 4, 2026 is Wednesday, July 14, 2027.

Federal holidays add about two more weeks. Nine of them fall inside that same window: Veterans Day, Thanksgiving, Christmas, New Year's Day, Martin Luther King Jr. Day, Washington's Birthday, Memorial Day, Juneteenth (observed Friday, June 18, 2027, because June 19 is a Saturday) and Independence Day (observed Monday, July 5, 2027, because July 4 is a Sunday). Skipping them moves the finish to Tuesday, July 27, 2027, which is 265 calendar days from the start. The OPM federal holiday schedule publishes the official list for each year.

Nothing here is fixed at eleven holidays or at 252 days. A window that crosses Thanksgiving and Christmas carries more days off than one that runs through summer, so treat 252 and 265 as estimates and then count the specific holidays your contract honors.

The 180 day clock inside a 1031 exchange

Section 1031 lets a real estate investor trade one property for another and postpone the capital gains tax, and the trade runs on two hard dates. The IRS instructions for Form 8824, 2025 revision, put it plainly: replacement property must be identified in writing within 45 days after you transfer the property you gave up, and it must be received within 180 days, or by the due date of your return including extensions, whichever comes first.

Take a closing on November 4, 2026. The 45 day identification deadline is Saturday, December 19, 2026, and the 180 day receipt deadline is Monday, May 3, 2027. Both are calendar days, and weekends do not move them, which is why a deadline can fall on a Saturday and stand.

The whichever comes first clause is the part people miss. A late December closing can leave fewer than 180 days, because an individual return filed in April would cut the window short unless the taxpayer files an extension. Read the deadline as the earlier of the two dates, never the later.

Six months, half a year and other near misses

People say six months when the paperwork says 180 days, and the two drift apart by a day or three. Six calendar months run 181 to 184 days depending on which months you cross and whether a leap day sits inside. From November 4, 2026, six months later is May 4, 2027, one day past the 180 day mark. From August 31, 2026, six months later is February 28, 2027, also one day past.

Half a year, meaning 182.5 days, sits two and a half days past 180. As a share of the year, 180 days covers 49.3 percent of a 365 day year and 49.2 percent of a leap year, which is why the phrase half a year and the number 180 never line up.

Other conversions worth keeping: 25 weeks and 5 days, 4,320 hours, 259,200 minutes, 15,552,000 seconds. Inside a 180 day window there are 128 or 129 weekdays and 51 or 52 weekend days, never a round number, and the split depends only on which weekday the window opens on.

Use the day count when a rule states days, and the month count when it states months. A visa rule or return window that says 180 days counts days, so matching the other side's convention is the whole game.

Counting backwards, and why two answers differ by a day

Lookbacks use the same arithmetic in reverse. 180 days before November 4, 2026 is Friday, May 8, 2026, and the weekday moves five places backward. Warranty windows, probation periods, lease lookbacks, insurance claim windows and the statement requests banks make all run in this direction.

One day disagreements come from convention, not arithmetic. A rule that says within 180 days of the event usually starts the clock the day after, which pushes the deadline one day later than subtracting 180 from the event date. A rule that counts the event day as day one lands one day earlier than this page. The federal unlawful presence rule is a useful test: it triggers at more than 180 days of presence, so day 181 is the first day that counts.

Time zones cause the other mismatch. A date is a calendar label, so this page does its arithmetic in UTC and never touches clock time, which keeps daylight saving out of the result. A phone set to a zone ahead of UTC can already show tomorrow's date at 9 pm local, and that is the date the input control hands over, so a deadline typed late at night can be one day off from the paper it came from.