TLTR

Use the /earliest_timestamp endpoint to determine the earliest available date and time for a specific security at a given interval.

Overview

The depth of historical data varies significantly based on the instrument type and interval. For equities, daily and higher intervals provide a complete history dating back to the first trading date, while intraday intervals typically range from a few months to a year.

Forex and cryptocurrencies also offer extensive daily historical data, with intraday data available for up to one year.

Refer to this article for best practices and techniques for retrieving historical data.