By default, Nikabot prompts you every day from Monday to Friday when you're active on Slack after 5 PM. Team admins can change the time for everyone, but you can also change it for yourself.
Changing the time for the daily prompt
You can change the Nikabot prompt time on your Profile page. You can also decide if you want Nikabot to ask you about the current or the previous day and if she should ask you even if you're away on Slack — otherwise, she'll wait until you get back online.
Remember that Nikabot uses your local timezone as defined on your Slack profile, make sure it's always correct.