How to change to correct time and date in Outlook calendar

[Chamomileteaplease]

Hi, I would be very grateful if someone could help me with this.

ATM, when a work colleague requests a meeting with me it comes through as for instance Sunday at 20:30 which is obviously not what they have suggested. (They put Monday at 09:30.)

Presumably my calendar is set up wrongly.

Can anyone let me know how to go in and reset my Outlook calendar?? Thank you!!!!