Timezone problem

I am at a time zone of GMT+8. I have properly set the Drupal's system at this time zone. Users will not have their own timezone. The OS (Linux) is set to UTC.

I use the "field validation" module and added the below rule on the reservation field:

Type: Date range 2
Column: value
Cycle of date: Global
Minimum date: now
Maximum date: empty

The field's Time zone handling is set to: "Sites' time zone".

Then when users create a new node of this type, this validator is triggered if the input time is within 8 hours from now. I printed the "Custom error message" with the [value] token, and found that the input date is 8 hours earlier than what the user input. i.e. if the user choose 09:00, the [value] prints 01:00. This means that the module does not consider the timezone offset when validating.