Bug fix for online order taking system

We used a freelancer to build a custom online order placement system for a wholesale bakery. It has been working perfectly for the last 5 months. Then this week, we are encountering a validation issue related to a date field. Specifically, in the place where a customer needs to enter the date for delivery (typically a week in advance), a dialog box pops up and says \"Date selected must be in the future\". But the dates being selected are in the future. Some future dates are ok, but the remainder get rejected.\r\n\r\nThe original coder on this project has done MIA. But we need someone to go through the code and fix the issue so orders can be submitted again. The code is written in php (as best I can tell). So we need someone who can quickly scan a bunch of code, understand how it works, identify the problem and then fix it.