Write a tax memo based on the following information:

Dave and Amandas form 1040 was audited and the IRS imposed a penalty they believed was incorrect. The taxpayers decided to petition the US Tax Court for relief, which required them to mail a petition form to the court. The deadline to mail the petition was April 5, 20xx. Dave and Amanda completed the petition and on April 5, 2018, placed it in an envelope that Amanda had stamped the same day using her employer's private postage meter. Amanda personally mailed the envelope at the Eugiene USPS office in Portland Oregon, late on April 5. The envelope had two postmarks, one dated April 5 from the private postage meter and one dated April 6 from the Eugiene post office. The Tax Court received the petition on April 12. The IRS filed a motion with the Tax Court to dismiss the taxpayers' petition because the deadline was missed. Dave and Amanda point out that the envelope with an April 5 Postmark, was carried into and mailed at the Eugiene Post Office on April 5. Is the petition "timely-filed" or are the taxpayers out of luck with their petition to appeal their tax bill?