How to use the relationship date calculator
Prepare the values for this calculation
Calculate completed relationship anniversary years and the next anniversary date. Use the formula below to check that it answers your question. Read the input units before transferring figures from a statement, measurement or dataset.
Enter and check each input
- Relationship start date: choose a real calendar date. The input uses year, month and day; confirm the date rather than entering an elapsed duration.
- As-of date: choose a real calendar date. The input uses year, month and day; confirm the date rather than entering an elapsed duration.
- Feb. 29 anniversary in non-leap years: choose Use February 28, Use March 1. Match this selection to the data you enter.
The input table gives a complete example. Keep units and time periods consistent across related fields.
Calculate and resolve any input error
Choose Calculate after entering the values. Changes also update the answer after a short pause. If an error appears, follow its message, correct the field and calculate again. Reset restores the example values.
Interpret the answer
Check Relationship anniversary first. With the unchanged example inputs, it is 6 completed years. Compare the additional metrics with the primary result; each has its own label and unit.
Compare and keep a useful result
The result diagram shows the inputs, method and output. A numeric chart is shown only when the calculation supports a meaningful numeric relationship.
Use Copy result or Download CSV to keep the answer. Share tool shares the page address without placing your input values in the URL. Recheck inputs and assumptions before using the result for a decision.
Relationship Date Calculator formula
Uses exact calendar dates and an explicit rule for Feb. 29 anniversaries.
Inputs and units
| Input | Format / range | Example |
|---|---|---|
| Relationship start date | YYYY-MM-DD | 2020-06-15 |
| As-of date | YYYY-MM-DD | 2026-10-06 |
| Feb. 29 anniversary in non-leap years | Select an option | Use February 28 |
Worked example
Using the example inputs above, the relationship anniversary is 6 completed years.
- Relationship anniversary
- 6 completed years
- Next anniversary
- 2027-06-15
- Days until next
- 252
Results and assumptions
The output uses the relationship anniversary convention and formula shown above. Match the entered units and source assumptions when comparing results.
Fix an input or unexpected result
If your answer differs from the example, choose Reset and compare every field, including selected units and options. Check percentage versus decimal entry and whether values describe the same period. Round only the final displayed answer when reproducing the formula.
If a discrepancy remains, report the calculator issue with the page address, non-sensitive example inputs, actual result, expected result and a reference for your calculation.