On Slack
If you are a Slack user, Nikabot gets the information about your time zone from your profile on Slack. You can check what time zone Nikabot thinks you're in by signing in and opening your Personal Preferences page or by typing help on a direct message with Nikabot. If you move to a different timezone, you should manually update your Slack profile. To do so, follow this link and edit your Time Zone.
On Teams
If you're a Teams user, you can set your timezone by using the set timezone command on your chat with Nikabot.
If you are a Nikabot admin and want to set the time zone for your whole team, you can use the set team timezone command on your chat with Nikabot.