General period planning
This calculator is a general repeating-period date tool. If you are using it for health, billing, legal deadlines or compliance, check the rules for inclusive dates, local time zones and professional guidance.
Example
Starting on May 17, 2026 with 28 days per period and 3 periods gives a total offset of 84 days. The calculator adds those days to the start date and shows the resulting calendar date.
Common mistakes
Do not confuse period length with number of periods. A 28-day period repeated 3 times is 84 days, not 31 days or three calendar months.
Limitations
The tool uses fixed day counts. It does not know medical cycles, subscription contract rules, billing grace periods, holidays or local legal deadline rules.
Last reviewed: 2026-05-17