Completions only happened from the dashboard with today's date.
The new Current task section on the series page lets users pick
the actual completion date before marking a task done.

Assisted-by: Claude Opus 4.6 via Claude Code

diff --git a/lib/ketchup/models.rb b/lib/ketchup/models.rb
index 910e3d2..fcfa46b 100644
--- a/lib/ketchup/models.rb
+++ b/lib/ketchup/models.rb
@@ -102,20 +102,20 @@ class Task < Sequel::Model
     days_overdue.to_f / interval
   end
 
-  def complete!(today:)
+  def complete!(completed_on:)
     DB.transaction do
-      update(completed_at: Time.now)
+      update(completed_at: Time.new(completed_on.year, completed_on.month, completed_on.day))
       next_date = case series.interval_unit
                   when "day"
-                    today + series.interval_count
+                    completed_on + series.interval_count
                   when "week"
-                    today + (7 * series.interval_count)
+                    completed_on + (7 * series.interval_count)
                   when "month"
-                    today >> series.interval_count
+                    completed_on >> series.interval_count
                   when "quarter"
-                    today >> (3 * series.interval_count)
+                    completed_on >> (3 * series.interval_count)
                   when "year"
-                    today >> (12 * series.interval_count)
+                    completed_on >> (12 * series.interval_count)
                   else
                     fail
                   end
diff --git a/lib/ketchup/views/series/show.rb b/lib/ketchup/views/series/show.rb
index e1d6794..87c7f9c 100644
--- a/lib/ketchup/views/series/show.rb
+++ b/lib/ketchup/views/series/show.rb
@@ -81,28 +81,53 @@ module Views
                     end
                   end
 
-                  if active_task
-                    dt { "Next due date" }
-                    dd(
-                      "x-show": "!editing",
-                      "x-text": "new Date('#{active_task[:due_date]}T00:00').toLocaleDateString()"
-                    ) { active_task[:due_date].to_s }
-                    dd(
-                      "x-show": "editing",
-                      "x-cloak": true,
-                      "x-data": "dueDateEditor(#{@series.id}, '#{active_task[:due_date]}')"
-                    ) do
-                      input(
-                        type: "date",
-                        class: "detail-input detail-input-date",
-                        "x-model": "dueDate",
-                        "x-on:change": "save()"
-                      )
+                end
+
+                if active_task
+                  complete_path = "/series/#{@series.id}/tasks/#{active_task.id}/complete"
+                  form(method: "post", action: complete_path, class: "current-task") do
+                    input(type: "hidden", name: "_csrf", value: @csrf.call(complete_path))
+                    input(type: "hidden", name: "return_to", value: "/series/#{@series.id}")
+                    div(class: "section-header") do
+                      h2(class: "section-title") do
+                        span(class: "section-title-text") { "Current task" }
+                      end
+                      button(type: "submit", class: "section-edit-btn") { "Complete" }
                     end
+                    dl(class: "detail-fields") do
+                      dt { "Due date" }
+                      dd(
+                        "x-show": "!editing",
+                        "x-text": "new Date('#{active_task[:due_date]}T00:00').toLocaleDateString()"
+                      ) { active_task[:due_date].to_s }
+                      dd(
+                        "x-show": "editing",
+                        "x-cloak": true,
+                        "x-data": "dueDateEditor(#{@series.id}, '#{active_task[:due_date]}')"
+                      ) do
+                        input(
+                          type: "date",
+                          class: "detail-input detail-input-date",
+                          "x-model": "dueDate",
+                          "x-on:change": "save()"
+                        )
+                      end
 
-                    if active_task.urgency > 0
-                      dt(class: "detail-overdue") { "Urgency" }
-                      dd(class: "detail-overdue") { "#{format("%.1f", active_task.urgency)}x" }
+                      if active_task.urgency > 0
+                        dt(class: "detail-overdue") { "Urgency" }
+                        dd(class: "detail-overdue") { "#{format("%.1f", active_task.urgency)}x" }
+                      end
+
+                      dt { "Completed on" }
+                      dd do
+                        input(
+                          type: "date",
+                          name: "completed_date",
+                          class: "detail-input detail-input-date",
+                          "x-data": true,
+                          "x-init": "$el.value = new Date().toISOString().slice(0, 10)"
+                        )
+                      end
                     end
                   end
                 end
diff --git a/lib/ketchup/web.rb b/lib/ketchup/web.rb
index 1c7293d..b7b13d3 100644
--- a/lib/ketchup/web.rb
+++ b/lib/ketchup/web.rb
@@ -147,7 +147,14 @@ class Web < Roda
           r.on "complete" do
             r.post do
               r.halt 422 unless @task[:completed_at].nil?
-              @task.complete!(today: Date.today)
+
+              completed_date = if (d = r.params["completed_date"]) && !d.empty?
+                Date.parse(d)
+              else
+                Date.today
+              end
+
+              @task.complete!(completed_on: completed_date)
 
               note_title = @series.note.lines.first&.strip || @series.note
               complete_path = "/series/#{series_id}/tasks/#{@task.id}/complete"
diff --git a/public/css/app.css b/public/css/app.css
index 9735dbd..65ad910 100644
--- a/public/css/app.css
+++ b/public/css/app.css
@@ -589,6 +589,14 @@ h2 { font-size: var(--step-0); font-weight: 600; }
   width: 100%;
 }
 
+/* -------------------- */
+/* Current task section */
+/* -------------------- */
+
+.current-task {
+  margin-block-start: var(--space-l);
+}
+
 /* -------------------- */
 /* Task history */
 /* -------------------- */
@@ -735,7 +743,7 @@ textarea {
   gap: var(--space-3xs);
 }
 
-button[type="submit"]:not(.complete-btn) {
+button[type="submit"]:not(.complete-btn):not(.section-edit-btn) {
   padding: var(--space-3xs) var(--space-s);
   border: 1px solid #1a1a1a;
   border-radius: 4px;
@@ -746,7 +754,7 @@ button[type="submit"]:not(.complete-btn) {
   cursor: pointer;
 }
 
-button[type="submit"]:not(.complete-btn):hover {
+button[type="submit"]:not(.complete-btn):not(.section-edit-btn):hover {
   background: #333;
 }
 
diff --git a/test/test_web.rb b/test/test_web.rb
index 02cbf7e..ef63dc9 100644
--- a/test/test_web.rb
+++ b/test/test_web.rb
@@ -207,7 +207,7 @@ class TestWeb < Minitest::Test
                   first_due_date: "2026-03-01")
 
     task = Task.first
-    task.complete!(today: Date.new(2026, 4, 1))
+    task.complete!(completed_on: Date.new(2026, 4, 1))
 
     new_task = Task.where(completed_at: nil).first
     assert_equal Date.new(2026, 4, 15), new_task.due_date