diff --git a/rfc2822.go b/rfc2822.go
index e511d75e..e02c1123 100644
--- a/rfc2822.go
+++ b/rfc2822.go
@@ -2,11 +2,12 @@ package mailgun
 
 import (
 	"strconv"
-	"strings"
 	"time"
+
+	"github.com/pkg/errors"
 )
 
-// Mailgun uses RFC2822 format for timestamps everywhere ('Thu, 13 Oct 2011 18:02:00 GMT'), but
+// RFC2822Time Mailgun uses RFC2822 format for timestamps everywhere ('Thu, 13 Oct 2011 18:02:00 GMT'), but
 // by default Go's JSON package uses another format when decoding/encoding timestamps.
 type RFC2822Time time.Time
 
@@ -35,15 +36,18 @@ func (t *RFC2822Time) UnmarshalJSON(s []byte) error {
 	if err != nil {
 		return err
 	}
-	if *(*time.Time)(t), err = time.Parse(time.RFC1123, q); err != nil {
-		if strings.Contains(err.Error(), "extra text") {
-			if *(*time.Time)(t), err = time.Parse(time.RFC1123Z, q); err != nil {
-				return err
-			}
-			return nil
+
+	var err1 error
+	*(*time.Time)(t), err1 = time.Parse(time.RFC1123, q)
+	if err1 != nil {
+		var err2 error
+		*(*time.Time)(t), err2 = time.Parse(time.RFC1123Z, q)
+		if err2 != nil {
+			// TODO(go1.20): use errors.Join:
+			return errors.Errorf("%s; %s", err1, err2)
 		}
-		return err
 	}
+
 	return nil
 }
 
diff --git a/rfc2822_test.go b/rfc2822_test.go
new file mode 100644
index 00000000..91348009
--- /dev/null
+++ b/rfc2822_test.go
@@ -0,0 +1,49 @@
+package mailgun
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/facebookgo/ensure"
+)
+
+func TestUnmarshalRFC2822Time(t *testing.T) {
+	type Req struct {
+		CreatedAt RFC2822Time `json:"created_at"`
+	}
+
+	tests := []struct {
+		name    string
+		s       string
+		want    Req
+		wantErr bool
+	}{
+		{
+			name:    "RFC1123",
+			s:       `{"created_at":"Thu, 13 Oct 2011 18:02:00 GMT"}`,
+			wantErr: false,
+			want:    Req{CreatedAt: RFC2822Time(time.Date(2011, 10, 13, 18, 2, 0, 0, time.UTC))},
+		},
+		{
+			name:    "RFC1123Z",
+			s:       `{"created_at":"Thu, 13 Oct 2011 18:02:00 +0000"}`,
+			wantErr: false,
+			want:    Req{CreatedAt: RFC2822Time(time.Date(2011, 10, 13, 18, 2, 0, 0, time.UTC))},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var req Req
+			err := json.Unmarshal([]byte(tt.s), &req)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("error = %v, wantErr %v", err, tt.wantErr)
+			}
+
+			ensure.True(t, time.Time(tt.want.CreatedAt).Equal(time.Time(req.CreatedAt)),
+				fmt.Sprintf("want: %s; got: %s", tt.want.CreatedAt, req.CreatedAt))
+		})
+	}
+}