Avoid <span> if you can and try elements designed for the job
Dates and times are formatted differently across the world and so cannot be reliably parsed by a search engine or email client. Specify what parts of a sentence are a time and allow programs to extract and use that information.
When wanting to highlight a few words of a sentence, it may seem best to use <strong>. While <strong> denotes importance, <mark> denotes relevance in the current situation. An example of this would be matched terms in a search result.
Language is full of abbreviations that readers potentially may not be familiar with – there’s plenty in this article! The <abbr> element provides a way to define potentially unfamiliar abbreviations with an accompanying ‘title’ attribute.
When quoting a small section of text, surround it with <q>. The optional ‘cite’ attribute can provide a name, reference or link to the original source. Browsers will add quote marks by default.
When providing instructions that should be input by a user, <kbd> should surround that command. While typically used for keyboard inputs it can be used for any kind of text entry, including voice.