When you request a candidate's availability, they'll choose the times based on their computer's current time zone. 

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When you view the availability request, the times will be calculated based on the timezone you selected for your user account. 

Interviewer_Time_Zone.png

If you ever want to check the candidate's time zone, it will be recorded at the top of their candidate profile.

Profile_Time_zone.png

When you schedule the interview, both your invite and your candidate's invite will have the correct times based on your respective time zones.

Note: Your time zone can be updated in your Greenhouse Recruiting user account.