The difference between day and night mode is whether the base station flashes light. The night mode is set for parents and babies who sleep sensitive to light. These people can get better rest in the night mode.
If you have any further questions, feel free to submit a request here, contact us via in-app Feedback (from the Sense-U App->Setup->Help->Feedback) for expedited diagnose, or email us at support@sense-u.com