Here are a few options for describing the WordPress post tag “寄出日期” in Traditional Chinese, depending on the nuance you want to convey:

**Option 1 (Most straightforward):**

> 文章標籤，用於標示郵寄或發貨的日期。
> *Wénzhāng biāoqiān, yòngyú biāoshì yóujì huò fāhuò de rìqí.*
> (Translation: Article tag, used to mark the date of mailing or dispatch.)

**Explanation:** This option is clear, concise, and directly explains the tag’s purpose.

**Option 2 (More detail, for internal documentation):**

> 此標籤用於標記與此文章相關的物件或商品寄出的日期。方便日後查找、追蹤郵寄紀錄，或整理訂單資訊。
> *Cǐ biāoqiān yòngyú biāojì yǔ cǐ wénzhāng xiāngguān de wùjiàn huò shāngpǐn jìchū de rìqí. Fāngbiàn rìhòu zhǎochá, zhuīzōng yóujì jìlù, huò zhěnglǐ dìngdān zīxùn.*
> (Translation: This tag is used to mark the date of dispatch for objects or goods related to this article. It facilitates future searching, tracking mailing records, or organizing order information.)

**Explanation:** This is more informative, explaining *why* the tag is used. Good for internal use or in a comprehensive blog description.

**Option 3 (Simple and functional):**

> 寄出日期，方便快速篩選與郵寄相關的文章。
> *Jìchū rìqí, fāngbiàn kuàisù shāixuǎn yǔ yóujì xiāngguān de wénzhāng.*
> (Translation: Mailing Date, for quickly filtering articles related to mailing.)

**Explanation:** This is a short, practical description that focuses on the tag’s functionality.

**Option 4 (Customer-facing, if applicable):**

> 查詢有關產品發貨日期的文章，請使用此標籤。
> *Cháxún yǒuguān chǎnpǐn fāhuò rìqí de wénzhāng, qǐng shǐyòng cǐ biāoqiān.*
> (Translation: To search for articles about product dispatch dates, please use this tag.)

**Explanation:** This option is more user-friendly and aimed at blog readers.

**Which one to choose?**

* If you’re primarily using the tag for your own organization, **Option 2** is best.
* If you have a more public-facing blog, consider **Option 1 or 3**.
* If you sell products and users need to track orders, **Option 4** would be suitable.

Make sure to choose the option that best fits the purpose of your WordPress blog and how you want to explain the tag to yourself or your users. Good luck!