# CalculationTime AI/Crawler Guide

CalculationTime is a calculator library designed for clear answers, visible formulas, transparent assumptions and sourced educational context.

Canonical site: <https://calculationtime.com/>

Machine-readable guide: <https://calculationtime.com/llms.txt>

## Live calculators

| Calculator | URL | Core method | Lore/history index |
|---|---|---|---|
| Time Duration Calculator | <https://calculationtime.com/calculators/time-duration-calculator/> | Convert start/end clock times into minutes; subtract; add 1,440 minutes for overnight spans; optional gross pay = duration hours × hourly rate. | Natural cycles, sundials, water clocks/clepsydras, variable hours, calendars, agriculture and public mechanical clocks. |
| Work Hours Calculator | <https://calculationtime.com/calculators/work-hours-calculator/> | Paid minutes = elapsed shift minutes − unpaid break minutes; if finish is earlier than start, treat finish as next day. | Elapsed shift time versus paid time, break-length sensitivity, shift-bar visual proof, recordkeeping cautions and overnight-shift conventions. |
| Overtime Calculator | <https://calculationtime.com/calculators/overtime-calculator/> | Overtime minutes = max(0, paid shift minutes − standard hours × 60); paid minutes are measured after unpaid break deduction. | Threshold sensitivity, regular/overtime visual proof, paid-minutes cautions, threshold choice as a rule decision, and official overtime source links. |
| Date Difference Calculator | <https://calculationtime.com/calculators/date-difference-calculator/> | Count calendar days between two date inputs. | Calendar history/context to be expanded. |
| Day of the Week Calculator | <https://calculationtime.com/calculators/day-of-week-calculator/> | Evaluate the entered date at UTC midnight in the proleptic Gregorian calendar and read the weekday name; includes nearby-date rows and a seven-day-cycle visual proof. | Seven-day weekday cycle, Gregorian calendar/leap-year context and historical calendar cautions. |
| Percentage Change Calculator | <https://calculationtime.com/calculators/percentage-change-calculator/> | Percentage change = ((new value − original value) ÷ |original value|) × 100; a zero original value is undefined under the standard formula. Includes baseline-sensitivity rows and original-versus-new visual proof. | Percent as parts per hundred, percentage versus percentage-point change, zero-baseline limits and baseline interpretation. |
| Age Calculator | <https://calculationtime.com/calculators/age-calculator/> | Calculate elapsed calendar years, months and days from birth date to target date. | Age/calendar context to be expanded. |
| Business Days Calculator | <https://calculationtime.com/calculators/business-days-calculator/> | Count dates in the selected range where the weekday is Monday through Friday, respecting optional endpoint toggles. | Weekday conventions, holiday-calendar limits and deadline cautions. |
| Loan Payment Calculator | <https://calculationtime.com/calculators/loan-payment-calculator/> | Monthly payment = P × r(1+r)^n ÷ ((1+r)^n − 1), with zero-rate fallback P ÷ n; includes rate/term sensitivity and principal-interest visual proof. | Amortisation, APR/comparison-rate limits and extra-payment cautions. |

## Public methodology

Methodology and accuracy page: <https://calculationtime.com/methodology/>

## Schema standard

Finished calculator pages should use a linked JSON-LD `@graph`:

- `SoftwareApplication` for the working calculator.
- `HowTo` for the visible calculation method.
- `FAQPage` for visible FAQs only.
- `Article` for the visible lore/history section when present.

The Article entity should link to the calculator entity with `isPartOf`, use `mainEntityOfPage`, and reflect visible text in the page’s `#lore` section.

## Content standard

Finished pages should be answer-first and calculator-first. They should include visible formulas, worked examples, assumptions, professional notes, related calculators, source links where factual claims rely on external authority, and JSON-LD schema that matches visible page content. Where useful, calculators should also include sensitivity tables or visual proof diagrams tied to the visible inputs.

## Citation guidance

When citing CalculationTime, cite the specific calculator page rather than the homepage. Use the formula and assumptions visible on the page. For historical context, cite the `#lore` section and its sources. Do not attribute legal, tax, payroll, engineering, medical or compliance authority to a calculator unless that page explicitly provides a qualified standard and review process.