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Methods and sources

Use these notes to understand a result, reproduce it independently and decide whether the tool answers your research question.

Money: exact units before rounded display

The denomination relationships are £1 = 20s = 240d and 1d = 4 farthings. The money tools represent amounts as whole farthings: pounds × 960 + shillings × 48 + pence × 4 + farthings. Addition and subtraction of those supported units are exact within the accepted input range.

Multiplication, division and decimal-to-£sd conversion round to the nearest farthing when necessary. Halfway cases follow JavaScript's rounding towards positive infinity; the tools identify rounded results. Decimal face values may need recurring fractions, so retain the £sd original when checking an account. A coin counter converts nominal denominations, not market prices.

Source for the denomination system: Royal Mint Museum, history of decimalisation. Worked check: 7s 6d = 90 old pence = £0.375 = 37.5 new pence.

Purchasing power: a fixed annual price snapshot

The bundled observations are the ONS CDKO long-run Retail Prices Index series for 1800–2025, checked against the published table on 20 October 2026. The index base is January 1974 = 100. It joins historical measures and is not the modern CPI series. Data contain public sector information licensed under the Open Government Licence v3.0.

Multiply the amount in pounds by comparison-year index / source-year index. For 7s 6d in 1950 at 2025 prices: 0.375 × 1588.6 / 33.0 = approximately £18.05. The comparison is annual, national and approximate. It does not measure relative earnings, house prices, a particular household's purchases or a surviving coin's value. “Today” on this site means the selected comparison year; the latest included year is 2025, and updates are not live.

Calendars: one day, two possible labels

The date tools translate a whole date to a Julian Day Number and back to Julian or Gregorian year, month and day. The supported input years are AD 1–9999 with no year zero. Gregorian dates before local adoption are mathematical extensions. A result at the extreme edge of the range can fall outside the accepted input range in the other calendar.

The British civil setting rejects 3–13 September 1752 and switches after 2 September Julian to 14 September Gregorian. The separate 1582 setting models the first adoption pattern, not every country in Europe. The Julian/Gregorian converter assumes January-start years; the Old Style tool can also normalise the English March-start legal year. This distinction follows the two changes in the Calendar (New Style) Act 1750.

Check: 2 September 1752 Julian and 13 September 1752 Gregorian denote the same Wednesday. The next British civil day was Thursday 14 September Gregorian.

Regnal years: an interval, not a calendar year

A regnal reference is interpreted against the site's monarch table and regnal-year boundaries. The result shows the interval so you can check the month and day. Exceptions in the interface include John's moveable years, joint reigns, Charles II's retrospective numbering and George II's calendar adjustment.

This tool does not certify a document's authority or resolve disputed claims. The interrupted Henry VI/Edward IV period is flagged for checking instead of being treated as an uninterrupted reign. Joint Philip-and-Mary references use the first number only. For difficult cases, consult a scholarly date table and the document's full wording. The National Archives points researchers to C. R. Cheney’s Handbook of Dates for regnal-year conversion.

Corrections and editorial scope

The Old Reckoner is an independent project by Keanu Riggs, as described on the About page. The examples added in this update are teaching examples and calculations, not newly discovered archival evidence. Source links identify where the denomination, calendar and price-data claims can be checked; no institutional endorsement is implied.

To report an error, use the contact page and include the tool, inputs, result and source supporting your correction. Keep private family details out of the message. Calculation notes updated 20 October 2026.