No worries, the IRS typically starts taking small amounts of stockpiled test returns prior to the official start date. Please note that your tax refund (if any) will not be processed until after January 28. To learn more please review the Tax Year 2018 Calendar.
Holly P has it right. Despite them accepting small runs to test software, no matter who says it on this or any other forum, returns were not officially accepted or starting to be worked on until today.