Don't require a special observance like April Fools to question the validity of online content. Do that all the time.
The only way to know whether something is true is to integrate it with your experience and/or experiment some more if needed.
BUT some content is designed to induce you to do that. Consider whether the source of the content has an incentive of making you waste time engaging with them (i.e. governments distracting you from real issues, or content farms publishing something wrong on purpose).