---
epic: 3
story: 3.3
title: "Historical Rates"
status: draft
---

## Epic 3 — Currency & Cryptocurrency
**Goal:** Real-time and historical currency conversion with 180+ fiat and 50+ crypto.

### Story 3.3: Historical Rates

As a CalcPad user,
I want to convert currencies using historical exchange rates on specific dates,
So that I can calculate what an amount was worth at a particular point in time.

**Acceptance Criteria:**

**Given** the expression `$100 in EUR on 2024-01-15`
**When** the engine evaluates it
**Then** it fetches (or uses cached) the EUR/USD rate from January 15, 2024
**And** the result reflects the historical conversion

**Given** historical rates for a specific date have been fetched before
**When** the same date is queried again
**Then** the cached historical rates are used without a network call

**Given** a historical rate result
**When** the result is displayed
**Then** the metadata clearly indicates "historical rate from [date]"
**And** it is visually distinct from live rate results

**Given** the expression `$100 in EUR on 1900-01-01` (a date before available data)
**When** the engine evaluates it
**Then** it returns a `CalcResult::Error` indicating historical rates are not available for that date

**Given** the device is offline and no cached historical rate exists for the requested date
**When** a historical conversion is requested
**Then** the engine returns a `CalcResult::Error` indicating the historical rate is not available offline

**Given** the expression `€500 in GBP on March 5, 2023`
**When** the engine evaluates it
**Then** it correctly parses the natural-language date format
**And** fetches the historical rate for 2023-03-05
