diff --git a/stats.go b/stats.go
index fd7d4ce9..4313eb93 100644
--- a/stats.go
+++ b/stats.go
@@ -5,6 +5,8 @@ import (
 	"time"
 )
 
+const iso8601date = "2006-01-02"
+
 type Stat struct {
 	Event      string         `json:"event"`
 	TotalCount int            `json:"total_count"`
@@ -32,7 +34,7 @@ func (m *MailgunImpl) GetStats(limit int, skip int, startDate *time.Time, event
 	}
 
 	if startDate != nil {
-		r.addParameter("start-date", startDate.Format(time.RFC3339))
+		r.addParameter("start-date", startDate.Format(iso8601date))
 	}
 
 	for _, e := range event {