More useful for supplementary error messages, not things that would need to display before user interaction.
Error messages should be short and simple. They should indicate what the user needs to do to resolve the error, not simply state that an error occurred. Bad example: “Invalid e-mail.” Good example: “Provide a complete e-mail address, like ‘yourname@example.com’.”
<form class="mzp-c-form mzp-is-error">
<div class="mzp-c-field ">
<label class="mzp-c-field-label"
for="s_event_date">Date</label>
<input class="mzp-c-field-control " type="text"
id="s_event_date" required aria-required="true"
value="March 3 '15"
aria-describedby="s_event_date-msg">
<div id="s_event_date-msg" class="mzp-c-field-msg"
role="tooltip">Must be in the format 2015-03-14.</div>
</div>
</form>