HTML <time> datetime Attribute

<p>I have a date on <time datetime="2017-02-14">Valentines day</time>.</p>

Dates:
<time datetime="1914">  <!-- means the year 1914 -->
<time datetime="1914-12">  <!-- means December 1914 -->
<time datetime="1914-12-20">  <!-- means 20 December 1914 -->
<time datetime="12-20">  <!-- means 20 December any year -->
<time datetime="1914-W15">  <!-- means week 15 of year 1914 -->

Date and Times:
<time datetime="1914-12-20T08:00">  <!-- means 20 December 1914 at 8am -->
<time datetime="1914-12-20 08:00">  <!-- also means 20 December 1914 at 8am -->
<time datetime="1914-12-20 08:30:45">  <!-- with minutes and seconds -->
<time datetime="1914-12-20 08:30:45.687">  <!-- with minutes, seconds, and milliseconds -->

Times:
<time datetime="08:00">  <!-- means 8am -->
<time datetime="08:00-03:00">  <!-- means 8am in Rio de Janeiro (UTC-3 hours)  -->
<time datetime="08:00+03:00">  <!-- means 8am in Madagascar (UTC+3 hours)  -->

Durations:
<time datetime="P2D">  <!-- means a duration of 2 days -->
<time datetime="PT15H10M">  <!-- means a duration of 15 hours and 10 minutes -->