DatedUnit

DatedUnit[unit, date] represents the specified unit at a specific date.

Examples

Currency at a specific date:

Quantity[100, DatedUnit["USDollars", {2020, 1, 1}]]

Convert historical currency:

UnitConvert[Quantity[100, DatedUnit["USDollars", {2010, 1, 1}]], "Euros"]

Please visit the official Wolfram Language Reference for more details.