jamiechong

When a WooCommerce product is on sale, a tag is placed on top of the Product Thumbnails. The default label for this tag is “Sale!”. 
This plugin allows you to customize the label and can even insert the price difference or percent difference. Examples:
<ul>
<li>Save 20%</li>
<li>20% off!</li>
<li>Save $5.00</li>
<li>$5.00 off!</li>
</ul>

Woocommerce Custom Sale Tag

Customize the sale tag that appears on WooCommerce product thumbnails when a product sale price is set lower than the retail price.

Mario Peshev

DevriX

DX Out of Date allows you to display a notification box on your posts 
when a given amount of time has passed. Quite handy when writing tutorials 
or any content that might get outdated due to external factors – now you 
could automatically notify your readers after a given period.
You can configure the expiration time of your posts in the admin panel. Valid time units are days, months and years.
Currently the plugin options are:
<ul>
<li>Period – “amount” of “duration” units (1 to 40)</li>
<li>Duration frame (days, months, years)</li>
<li>Message – the message format for the notification box</li>
<li>Enable by default – a checkbox for enabling the message on all posts by default</li>
<li>Enable post status in Dashboard – a checkbox for adding an extra column in the Dashboard for the outdated status of posts</li>
<li>Post types to affect – allows you to choose which post types for display the message for</li>
<li>Position of the message – choose whether the message should be displayed at the top or at the bottom of a post’s content</li>
<li>Background color – Choose a background color for the message</li>
<li>Text color – Choose a text color for the message</li>
<li>Custom CSS – Add custom CSS rules to the message box</li>
</ul>

DX Out of Date

Display a notification box on the single view of your outdated posts, given a set amount of time (configurable).

Woocommerce Custom Sale Tag vs DX Out of Date