Cryptocurrencies use the UTC timezone by default.

Forex uses Australia/Sydney timezone by default.

All other instrument types, such as equities, ETFs, indices, etc. - use the exchange's timezone. See the below table for an idea:

Endpoints containing the datetime field in response can be converted to the timezone that matches your usage case. The modification is done via the &timezone parameter, and complete documentation can be seen by clicking the Advanced button in the documentation.

For instance, to get Apple Inc time series data in Central European Time (CET), use the following query:

https://api.twelvedata.com/time_series?symbol=AAPL&interval=1min&timezone=Europe/Zurich&apikey=demo