| Invalid date | A non-existent date or wrong format was entered | Check day, month and year, including month length and leap-year validity. |
| Age looks negative | The birth date follows the chosen as-of date | Check DOB and reference date; select a date after birth. |
| Age off by one year | Birthday has not yet occurred in the chosen year | Compare month/day rather than subtracting birth year alone. |
| Months and days do not match a rough estimate | Months vary from 28 to 31 days | Trust calendar-based subtraction after verifying both dates. |
| Time totals seem inaccurate | Birth time was omitted or a timezone assumption differs | Enter accurate time if known and check device clock and time zone. |
| Countdown shows unexpected hours | Local midnight versus birth time convention | Confirm time field and reference timezone. |
| Next birthday seems a year away | The birthday already passed or is considered today | Check the reference date and countdown rollover. |
| February 29 birthday behaves differently | Non-leap-year anniversary convention | Choose the relevant civil or institutional rule for your use case. |
| Days differ by one | Inclusive versus exclusive date counting | Check whether the first and last dates are counted. |
| Business days too high | Public holidays are not subtracted | Use the official holiday calendar and adjust manually. |
| School eligibility conflicts with a website | Different published cutoff or policy | Check the school’s exact year, district and cutoff date. |
| Retirement date seems wrong | Chosen retirement age differs from scheme rule | Verify pension plan and employment policy. |
| Two-person age gap looks wrong | Dates were entered in the wrong order or format | Review both dates and compare the absolute gap. |
| Pet years differ from other sources | Different heuristic models are used | Read model assumptions and ask a veterinarian for care guidance. |
| Planetary age seems surprisingly large | Shorter orbital period than Earth | Check the chosen planet and its orbital-year length. |
| Chinese zodiac differs near New Year | Gregorian and lunar-year boundaries differ | Verify the lunar-year transition for that exact birth date. |
| Heartbeats look unrealistic | Fixed population-average rate was assumed | Treat lifetime life statistics as illustrative only. |
| Biological age conflicts with health records | Simplified lifestyle estimation | Do not use it clinically; seek professional advice if needed. |
| Pregnancy due date differs from ultrasound | LMP assumptions or cycle variation | Use your healthcare provider’s clinical date. |
| Saved event is missing | Browser cache or site data was cleared | Restore from an exported backup if available and save records externally. |
| Saved dates are missing on another device | Storage is local to the browser | Export and transfer data using permitted workflow. |
| PDF layout is unexpected | Export formatting and fonts vary | Open the PDF and review before sharing. |
| CSV date is changed in Excel | Spreadsheet auto-conversion of date format | Import CSV as text or explicitly choose date format. |
| Share link reveals dates | Date values can be encoded in the URL | Inspect the link contents and use private sharing. |
| No response from calculator | Required input missing or scripts blocked | Provide a valid date, enable JavaScript and reload. |
| Calculator shows a different current date | Device clock or timezone differs | Check device date and timezone. |
| Future age is not today’s age | A custom as-of date remains selected | Reset the reference date to today. |
| Work anniversary count is incorrect | Wrong employment start date entered | Verify the service start date and any employment breaks. |
| Milestone date appears early | Counted elapsed calendar days versus completed days | Check the rule and birth-time assumption. |
| Export button does not work | Browser download permission or pop-up blocking | Check permissions and try supported browser export again. |