# CalculationTime AI/Crawler Guide
CalculationTime is a calculator library designed for clear answers, visible formulas, transparent assumptions and sourced educational context.
Canonical site:
Machine-readable guide:
## Live calculators
| Calculator | URL | Core method | Lore/history index |
|---|---|---|---|
| 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 | | 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 | | 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. |
| Payroll Time Card Calculator | | Paid shift hours = max(0, shift length hours − unpaid break minutes ÷ 60); weekly paid hours = sum of paid shifts; overtime hours = max(0, weekly paid hours − threshold); simple gross pay = regular hours × rate + overtime hours × rate × multiplier. | Daily shift evidence, weekly threshold sensitivity, regular/overtime visual proof, payroll-rule cautions and gross-pay limitations. |
| Date Difference Calculator | | Count calendar days between two date inputs. | Calendar history/context to be expanded. |
| Date Calculator | | Result date = start date at UTC midnight + (days to add or subtract × 86,400,000 milliseconds). Includes one-week sensitivity rows and a start-to-result timeline proof. | Elapsed calendar-day arithmetic, UTC-midnight date handling, inclusive-counting cautions and business-day/legal-deadline separation. |
| Day of the 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 | | 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. |
| Percent Calculator | | Percent = (part value ÷ whole value) × 100; a zero whole is undefined because division by zero is not valid. Includes denominator sensitivity rows and a part-of-whole visual proof. | Percent as parts per hundred, denominator context and zero-whole safeguards. |
| Age Calculator | | Calculate elapsed calendar years, months and days from birth date to target date. | Age/calendar context to be expanded. |
| 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 | | 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. |
| Hours to Decimal Calculator | | Total seconds = hours × 3,600 + minutes × 60 + seconds; decimal hours = total seconds ÷ 3,600; decimal minutes = total seconds ÷ 60. Includes rounding-increment sensitivity and an hour-segment visual proof. | Decimal time for timesheets, billing and project logs; preserves raw duration before any workplace/client rounding rule. |
| Time Calculator | | Base seconds = hours × 3,600 + minutes × 60 + seconds; signed change seconds use the same units; result seconds = base seconds + change seconds, then normalise into days, hours, minutes and seconds. Includes final-adjustment sensitivity and base-versus-result visual proof. | Duration arithmetic through total seconds; useful for logs, media lengths, sports splits and task totals, while keeping clock-time/timezone rules separate. |
| Timezone Meeting Calculator | | UTC minutes = source local minutes − source UTC offset × 60; target local minutes = UTC minutes + target UTC offset × 60, then normalise into a 24-hour clock and date-shift note. Includes target-offset sensitivity and a local-to-UTC-to-target visual proof. | UTC as shared reference, manual fixed offsets versus full city timezone/DST rules, and previous-day/next-day meeting traps. |
| Feet and Inches to Metres and Centimetres Calculator | | Total inches = feet × 12 + inches; metres = total inches × 0.0254; centimetres = metres × 100. Basis: the international inch is exactly 25.4 mm / 0.0254 m. Includes allowance what-if rows and a metric length-bar visual proof. | Exact inch/metre conversion, preserving original imperial dimensions with metric records, and separating arithmetic precision from material tolerance. |
| Metres and Centimetres to Feet and Inches Calculator | | Total centimetres = metres × 100 + centimetres; total inches = total centimetres ÷ 2.54; feet = floor(total inches ÷ 12); remaining inches = total inches − feet × 12. Basis: the international inch is exactly 25.4 mm / 2.54 cm. Includes small-allowance what-if rows and an imperial length-bar visual proof. | Exact centimetre/inch conversion, preserving original metric dimensions beside practical feet-and-inches readings, and rounding only after tolerance is chosen. |
## Public methodology
Methodology and accuracy page:
## 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.