An upcoming milestone result can show today. That is useful when you want to know whether you are currently on Day 100 rather than which milestone comes strictly afterward.
Reproduce a milestone day
Set Relationship Start Date to January 1, 2025 and Calculate Until Date to April 10, 2025. The tool shows 99 elapsed days and inclusive Day 100. Choose Inclusive day numbers and the next 100-day milestone is April 10 itself.
If you change the reference date to April 11, the inclusive count becomes Day 101. The next multiple of 100 is then Day 200, which falls on July 19. This is a milestone sequence. It does not restart each calendar year.
Keep the convention visible
With elapsed counting, the 100-day target for the same start is April 11. When saving an event, use a title such as “Day 100 together” or “100 completed days together” and put the counting convention in its note.
For reminders about a milestone you already celebrated, retain the one-time event if you want a record. Annual repeat would turn a fixed day count into a calendar anniversary with a different meaning.
The tool's anniversary result remains anchored to January 1 regardless of the selected day-count convention.