How to remove part of line from HTML file

Question

I have a file, events.html, containing similar lines (among many other):

<td class="EventDate">2021-08-06 12:36:34</td>

where date and time strings are different in each line.
In these lines there are ONLY class="EventDate"
Like to remove from every such line ONLY time string.

Additional info:

• system is Debian 9.13 64 bit
• file is 38kb long
• there are about 100 records, each comprising line similar to
  <td class="EventDate">2021-08-06 12:36:34</td>
  BUT date and time strings are different in each line!
• file contain near the end only one line with (example!)
  date and time: [2021-08-08 14:16:54 UTC]

For security reasons can not post whole file.

I am neither IT professional nor Linux Guru
but capable of performing various demanding tasks.

Answer 1

Using xmlstarlet to edit the file, updating the value with an xpath expression:

xmlstarlet ed -u '//td[@class="EventDate"]' -x 'substring-before(.," ")' events.html

Add -L to perform the edits in-place instead of writing the result to standard output.

Ex. given

$ cat events.html 
 <table>
  <tr>
    <td>Cell A</td>
    <td class="EventDate">2021-08-06 12:36:34</td>
  </tr>
  <tr>
    <td>Cell C</td>
    <td class="OtherDate">2021-08-06 12:36:34</td>
  </tr>
</table>

then

$ xmlstarlet ed -O -u '//td[@class="EventDate"]' -x 'substring-before(.," ")' events.html 
<table>
  <tr>
    <td>Cell A</td>
    <td class="EventDate">2021-08-06</td>
  </tr>
  <tr>
    <td>Cell C</td>
    <td class="OtherDate">2021-08-06 12:36:34</td>
  </tr>
</table>