Do you use the app by any chance? I had similar probs which I resolved by logging in via the browser and changing the time zone settings. There's more setting options via the browser than there is through the app. Hope that helps.
Only cuz that is what you set it at. All users can set their timezone preferences on the website/app by logging in to your User CP (from a browser) and going to Edit Options. Then scroll down and go to the Date and Time Options. From here you can choose your timezone: You can choose the day the weeks start and whether to auto correct for daylight savings time.