The number/user time zone defines the availability of the user or number.
When you set the custom availability on the number/user, the system will place calls as per the availability in the particular time zone set from which that user belongs.
The user will be able to see all the calls and reports as per his time zone.
For eg :- If the user has set the Indian Standard time zone, he will see the time of call made or received as per his IST. The call report will also be as per IST irrespective of the number’s time zone.
Your timezone is shown on the Open Hours feature in Number Settings of a number:-
Your timezone is shown on the Availability feature in User Settings of a user :-
NOTE:- You can change the timezone by clicking on the Edit button placed next to the display of the time zone. Then select the time zone that you’re in from the options presented in the drop-down box as shown below.