# Data Explanations
source: https://developer.mastercard.com/enhanced-currency-conversion-calculator/documentation/tutorials-and-guides/data-explanations/index.md

This page explains the key data elements, formats, and domain terminology used across the Enhanced Currency Conversion Calculator API, beyond the field-by-field glossary in [Parameters](https://developer.mastercard.com/enhanced-currency-conversion-calculator/documentation/parameters/index.md).

## Mastercard Currency Conversion Rates {#mastercard-currency-conversion-rates}

Mastercard publishes currency conversion rates once per day, and the rates are effective for a 24-hour period. Mastercard foreign exchange rates are specific to the date and time the issuing bank authorizes the transaction (which generally occurs at the point of sale/interaction). For certain transactions --- including those submitted to Mastercard for processing nine or more days after the original date of authorization --- Mastercard applies the foreign exchange rate in effect at the date and time it processes the transaction rather than the original authorization date.

* To retrieve the rate effective at the time of the request, some Mastercard services accept a placeholder date; for this API, always provide the specific `rate_date` you want rates for, in `yyyy-MM-dd` format.
* Use [Rate Publication Status Tutorial](https://developer.mastercard.com/enhanced-currency-conversion-calculator/documentation/tutorials-and-guides/rate-publication-status-tutorial/index.md) to confirm a date's rates are published before requesting them.
* For more information about Mastercard currency conversion rates, refer to the core manuals available on [Mastercard Connect](https://www.mastercardconnect.com/mccpblcui/#/public/signin) \> [Technical Resource Center](https://techdocs.mastercard.com/category/references).

## European Central Bank (ECB) Reference Rates {#european-central-bank-ecb-reference-rates}

The API supports all euro foreign exchange reference rates currently published by the [European Central Bank](https://www.ecb.europa.eu/stats/policy_and_exchange_rates/euro_reference_exchange_rates/html/index.en.html) (ECB). All ECB currencies are quoted against the euro (the base currency).

* The API is usually updated within one hour after the ECB publishes its new reference rates, at 16:00 Central European Time.
* If the ECB does not publish reference rates for a given date (for example, a TARGET closing day), the API returns the last published rate instead.
* When neither the transaction currency nor the cardholder billing currency is the euro, the API derives a calculated reference rate from the two ECB rates for those currencies.

## Percentage Difference Calculations {#percentage-difference-calculations}

The API returns two percentage-difference fields, both comparing the Mastercard rate to the ECB reference rate for the same currency pair:

|                   Field                    |                                                       Compares                                                       |
|--------------------------------------------|----------------------------------------------------------------------------------------------------------------------|
| `pctDifferenceMastercardExclAllFeesAndEcb` | Mastercard's rate **excluding** issuer fees, against the ECB reference rate.                                         |
| `pctDifferenceMastercardInclAllFeesAndEcb` | The **effective** conversion rate, **including** issuer fees (fixed and percentage), against the ECB reference rate. |

This is the figure most issuers use for the EU 2019/518 disclosure --- see [Cardholder FX Disclosure](https://developer.mastercard.com/enhanced-currency-conversion-calculator/documentation/use-cases/cardholder-fx-disclosure/index.md).

## Reference Documents {#reference-documents}

Further background is available in the following documents, on [Mastercard Connect](https://www.mastercardconnect.com/mccpblcui/#/public/signin) \> [Technical Resource Center](https://techdocs.mastercard.com/category/references):

|                                                                                                               Document                                                                                                               |           Description            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------|
| [Mastercard Rules](https://trc-techresource.mastercard.com/r/bundle/m_mcrs_en-us/page/d/en-US/hrc1744216454865.html)                                                                                                                 | Mastercard rules and standards.  |
| [Authorization Manual](https://trc-techresource.mastercard.com/r/bundle/m_AP_en-us/page/d/en-US/osq1748371604832.html)                                                                                                               | Mastercard core manuals.         |
| [Global Clearing Management System Reference Manual](https://trc-techresource.mastercard.com/r/bundle/m_gcmsrefmanual_en-us/page/d/en-US)                                                                                            | Mastercard core manuals.         |
| [AN 3493 Enhanced Currency Conversion API and Pricing for Issuers in the EEA Countries](https://techdocs.mastercard.com/announcements?labelkey=type_announce&labelkey=type_bulletin_announce&sort.field=last_revised&sort.value=dec) | Pricing and billing information. |