diff --git a/modules/gcal/cal_event.go b/modules/gcal/cal_event.go
index 2c1223008..2884af125 100644
--- a/modules/gcal/cal_event.go
+++ b/modules/gcal/cal_event.go
@@ -49,8 +49,13 @@ func (calEvent *CalEvent) Now() bool {
 
 func (calEvent *CalEvent) Past() bool {
 	if calEvent.AllDay() {
-		// FIXME: This should calculate properly
-		return false
+		now := time.Now().Local()
+		todayMidnight := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
+
+		// All-day event end dates are exclusive (Google Calendar convention: a
+		// single-day event starting on the 3rd has an end date of the 4th), so
+		// the event is past once its end date's midnight is today or earlier.
+		return !calEvent.End().After(todayMidnight)
 	}
 
 	return !calEvent.Now() && calEvent.Start().Before(time.Now())
diff --git a/modules/gcal/cal_event_test.go b/modules/gcal/cal_event_test.go
new file mode 100644
index 000000000..079ee4d2b
--- /dev/null
+++ b/modules/gcal/cal_event_test.go
@@ -0,0 +1,72 @@
+package gcal
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"google.golang.org/api/calendar/v3"
+)
+
+func allDayEvent(startDate, endDate string) *CalEvent {
+	event := &calendar.Event{
+		Start: &calendar.EventDateTime{Date: startDate},
+		End:   &calendar.EventDateTime{Date: endDate},
+	}
+	return NewCalEvent(event)
+}
+
+func Test_Past_AllDayEvent(t *testing.T) {
+	yesterday := time.Now().AddDate(0, 0, -1)
+	today := time.Now()
+	tomorrow := time.Now().AddDate(0, 0, 1)
+
+	dateOnly := func(d time.Time) string {
+		return d.Format("2006-01-02")
+	}
+
+	testCases := []struct {
+		name       string
+		startDate  string
+		endDate    string
+		pastWanted bool
+	}{
+		{
+			name:       "single-day all-day event yesterday is past",
+			startDate:  dateOnly(yesterday),
+			endDate:    dateOnly(today),
+			pastWanted: true,
+		},
+		{
+			name:       "single-day all-day event today is not past",
+			startDate:  dateOnly(today),
+			endDate:    dateOnly(tomorrow),
+			pastWanted: false,
+		},
+		{
+			name:       "single-day all-day event tomorrow is not past",
+			startDate:  dateOnly(tomorrow),
+			endDate:    dateOnly(tomorrow.AddDate(0, 0, 1)),
+			pastWanted: false,
+		},
+		{
+			name:       "multi-day all-day event ending yesterday is past",
+			startDate:  dateOnly(yesterday.AddDate(0, 0, -2)),
+			endDate:    dateOnly(yesterday),
+			pastWanted: true,
+		},
+		{
+			name:       "multi-day all-day event spanning today is not past",
+			startDate:  dateOnly(yesterday),
+			endDate:    dateOnly(tomorrow),
+			pastWanted: false,
+		},
+	}
+
+	for _, tt := range testCases {
+		t.Run(tt.name, func(t *testing.T) {
+			event := allDayEvent(tt.startDate, tt.endDate)
+			assert.Equal(t, tt.pastWanted, event.Past())
+		})
+	}
+}