What timezone are you in? It shouldn't matter but the datepicker might be in your timezone but the date then selected in the hotel's, if you're in Hong Kong it might be 2am on the 23rd but 10am or something on the 22nd in the US location, and while you select the 7th the system then recalculates that to US timezone which ends up being the 6th. It's wrong but it could happen.
EDIT: sorry I see hotel is in SIN, bit still might be because of some issue like that, server time likely is US time.