There's no date on this letter.

这封信未注明日期。

《牛津词典》

Even so, this is where your reader is going to look to find your address and the date the letter was written, so it should be there.

尽管这样，当读信人想知道信来自何方，以及写于何时，他们仍会到这里去查找。所以现在也仍要这样写。

youdao

Your letter of the.. crossed ours of the same date.

贵方…月…日函刚好错过我方同日信函。

youdao

The university asked me to provide an up-to-date sponsor letter, which I couldn't get hold of because of the situation in Syria.

BBC: Syrian students face fees crisis

Although the Notice of Claim Disallowance letter sent by the Service generally contains a statement advising the taxpayer that the two-year period began on the date of the letter, the Service occasionally mails these letters without the paragraph notifying the taxpayer of the two-year period for filing suit.

FORBES: When It Comes to the Two Year Statute - You are on Your Own

Yesterday, key government officials, trade stakeholders, and members of the press were on hand to witness U.S. Trade Representative Ron Kirk and Panamanian Minister of Commerce and Industry Ricardo Quijano sign a letter exchange setting a date for the entry-into-force of the U.S.-Panama Trade Promotion Agreement (TPA).

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