How this calculator works
Ninety days is a familiar probation length, performance-plan period and visa window. The calculator moves by ninety whole calendar days, which is not the same as three calendar months: a quarter can be 90, 91 or 92 days depending on which months it covers. The weekdays-inside count is a planning aid and includes no holiday exclusions; use the day counter if you need to remove specific weekdays or Canadian federal holidays.
Formula
result = fromOrdinal(O(start date) + 90) forward, or fromOrdinal(O(start date) - 90) backward. The span is 12 weeks and 6 days. Weekdays inside counts Monday to Friday dates after the earlier endpoint through the later endpoint.
Worked example
90 days after 2026-11-01 is 2027-01-30, a Saturday. The span is 12 weeks and 6 days with 65 weekdays inside. 90 days before 2026-11-01 is 2026-08-03, a Monday.
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Frequently asked questions
Is 90 days a quarter?
Usually not exactly. A calendar quarter runs from the first of one quarter month to the day before the same date three months later, which is 90 to 92 days. Ninety days is a fixed interval, so it is the right tool when a policy names days rather than quarters.
What is a 90-day probation period?
It is a trial period, common in employment and benefits, during which different rules may apply. The end date depends on whether the first day of work counts and whether the period follows calendar or working days, so confirm the wording in the contract.
Why does the result land on a Saturday?
Adding a multiple of seven preserves the weekday, but 90 is 12 weeks plus 6 days, so the weekday moves six places. A deadline that falls on a weekend may roll to the next business day under some rules and not others.