Yes, you should take the IRS information as the most accurate. You can rely on Where's my refund? for updates on your refund. The only additional option is to call the IRS and ask them about your refund. Follow this link for contact info.
When you refer to "estimated refund", I assume you are talking about the date TurboTax originally estimated your refund would come. This is a guess based on the experiences of most people in the past.
You estimated date won't ever change, because once your e-file is accepted by the IRS, TurboTax never gets any updated information beyond that point.
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