You could even do it without Scratch:
{{ $future_content := slice }}
{{ $date_format := "2006-01-02T15:04:05" }}
{{ range where .Site.RegularPages "Section" "events" }}
{{ $formatted_start := (time .Params.start).Format $date_format }}
{{ $formatted_now := now.Format $date_format }}
{{ if ge $formatted_start $formatted_now }}
{{ $future_content = $future_content | append . }}
{{ end }}
{{ end }}
{{ range $future_content }}
{{ . }}
{{ end }}
Then replace that last range with your pageinator code.