Let me take a moment to provide a public-service announcement:
when·ev·er /(h)wenˈevər,(h)wəˈnevər/ conjunction: at whatever time; on whatever occasion (emphasizing a lack of restriction). “You can ask for help whenever you need it.” Every time that. “The springs in the armchair creak whenever I change position.” Adverb: used for emphasis instead of “when” in questions, typically expressing surprise or confusion. “Whenever shall we get there?” Or whenever — or at any time. “If you lay eyes on him, either tonight or tomorrow or whenever, call me right away.”
when /(h)wen/ adverb: at what time. “When did you last see him?” How soon. “When can I see you?” In what circumstances. “When would such a rule be justifiable?” At or on which (referring to a time or circumstance). “Saturday is the day when I get my hair done.” Conjunction: 1. at or during the time that. “I loved math when I was in school.” After. “Call me when you’re finished.” At any time that; whenever. “Can you spare five minutes when it’s convenient?” 2. after which; and just then (implying suddenness). “He had just drifted off to sleep when the phone rang.” 3. in view of the fact that; considering that. “Why bother to paint it when you can photograph it with the same effect?” 4. although; whereas. “I’m saying it now when I should have told you long ago.”
Here are a couple of example sentences of how not to use the word “whenever”:
“Whenever I was in high school, I would go out with my friends on Friday nights.”
“I saw him at the post office whenever I checked my mail on Tuesday” (assuming you only went to check your mail once that day).
This really should be all of the explanation necessary, and yet I get the feeling it will do no good.