If you wake up on December 31 in Hawaii, let’s say at 9am, all of the Australia and Asia have celebrated New Year already, it’s January 1st for them already. So it’s not so simple and obvious, what’s today’s date! It really depends on your location.
Now you can set your hotels location (hence hotels local time) in this booking software. What does it affect? It makes booking calender work perfectly in your timezone, calendar’s “today” is really today, it does not matter any more, what our server’s clock is.