What it sounds like
Event date group, From day, 1, combo box
In this case, the from and to dates form one logical group, and should all be in one fieldset.
What it looks like
<fieldset>
<legend class="visuallyhidden">Event date</legend>
<span>From</span>
<select
aria-label="From day"
id="event-date-from-day"
name="event-date-from-day"
>
<option>1</option>
<option>etc</option>
</select>
<select
aria-label="From month"
id="event-date-from-month"
name="event-date-from-month"
>
<option>January</option>
<option>etc</option>
</select>
<select
aria-label="From year"
id="event-date-from-year"
name="event-date-from-year"
>
<option>2020</option>
<option>etc</option>
</select>
<span>To</span>
<select aria-label="To day" id="event-date-to-day" name="event-date-to-day">
<option>1</option>
<option>etc</option>
</select>
<select
aria-label="To month"
id="event-date-to-month"
name="event-date-to-month"
>
<option>January</option>
<option>etc</option>
</select>
<select
aria-label="To year"
id="event-date-to-year"
name="event-date-to-year"
>
<option>2020</option>
<option>etc</option>
</select>
</fieldset>