It helps to split it up:
{{/* Get Posts */}}
{{ $posts := where site.RegularPages "Type" "post" }}
{{/* Group Posts by Date */}}
{{ $grouped := $posts.GroupByDate "2006-01-02" }}
{{/* Paginate Group */}}
{{ $paginated := (.Paginate ($grouped)) }}
{{/* Range over Page Groups */}}
{{ range $paginated.PageGroups }}
{{/* Range over PageGroup Pages (in Reverse) */}}
{{ range .Pages.Reverse }}
{{ .Render "summary"}}
{{ end }}
{{ end }}
See: