How it is calculated
We add years, then months, then weeks and days. When adding months, if the same day does not exist in the resulting month (e.g. the 31st), the last day of that month is used.
Result = date + years + months + (weeks × 7 + days)Worked example
21 October 2026 + 90 days = 19 January 2027 (Tuesday).
Frequently asked questions
Are 3 months the same as 90 days?
Not always — 3 calendar months can be 89 to 92 days. Use the unit your contract states.
How do I subtract?
Choose “subtract” or enter a negative number.
Are holidays counted?
Yes, these are calendar days. For working days use the business days calculator.