A 120-day span covers roughly four months, and it’s long enough to show up in bigger planning horizons — a construction timeline, a long-lead visa or immigration process, a wedding planning countdown, or the standard window some medical trials use for a follow-up assessment. At this length, the exact landing date is noticeably sensitive to which four (or so) months the count happens to pass through, since some run of months adds up to more total days than another.
Finding the date works the same way it does for any shorter offset, just extended further: start today and count forward 120 individual calendar days, rolling from one month into the next whenever the current month’s days run out, and crossing into a new year if the span reaches past December. For example, if today were March 3rd, the count would use the remaining 28 days of March, all 30 of April, all 31 of May, all 30 of June, leaving 1 day left over — landing on July 1st. Shift the starting point by even a few weeks and the total distance covered by “120 days” changes, because different months are involved.
That sensitivity is exactly why a tool that counts real calendar days is more reliable than mentally adding “about four months” to today’s date — the difference can easily be several days depending on which months of the year the span falls in, and for a deadline that’s been circled on a calendar for months in advance, getting the exact date right matters.