added leap year test

also use method chaining for date manipulation

pkg/server/warcserver/daterange.go

@@ -102,12 +102,10 @@ func To(t string) (int64, error) {
 
 	switch tLen {
 	case 4:
-		to = to.AddDate(0, 12, -1) // 31 days in decemeber
-		to = to.Add(time.Hour*23 + time.Minute*59 + time.Second*59)
+		to = to.AddDate(0, 12, -1).Add(time.Hour*23 + time.Minute*59 + time.Second*59)
 	case 6:
 		// add one month - one day, i.e: user supplies january, we add 29 - 1
-		to = to.AddDate(0, 1, -1)
-		to = to.Add(time.Hour*23 + time.Minute*59 + time.Second*59)
+		to = to.AddDate(0, 1, -1).Add(time.Hour*23 + time.Minute*59 + time.Second*59)
 	case 8:
 		to = to.Add(time.Hour*23 + time.Minute*59 + time.Second*59)
 	case 10:

pkg/server/warcserver/daterange_test.go

@@ -134,6 +134,20 @@ func TestFromAndToParsing(t *testing.T) {
 			23*60*60 + 60*59 + 59,
 			false,
 		},
+		{
+			"normal year date string succeeds",
+			"197002",
+			time.Date(1970, 2, 1, 0, 0, 0, 0, time.UTC).Unix(),
+			time.Date(1970, 2, 28, 23, 59, 59, 0, time.UTC).Unix(),
+			false,
+		},
+		{
+			"leap year date string succeeds",
+			"200002",
+			time.Date(2000, 2, 1, 0, 0, 0, 0, time.UTC).Unix(),
+			time.Date(2000, 2, 29, 23, 59, 59, 0, time.UTC).Unix(),
+			false,
+		},
 		{
 			"empty date string succeeds",
 			"",