minor improvement of the x/jsonx.SimpleDate time parser

more features designed for the past 2-3 months to come, this is just a hotfix

x/jsonx/simple_date_test.go

@@ -57,3 +57,37 @@ func TestSimpleDateAterBefore(t *testing.T) {
 		t.Fatalf("[after] expected d2 to be after d1")
 	}
 }
+
+func TestCountPastDays(t *testing.T) {
+	tests := []struct {
+		AfterDate        SimpleDate
+		BeforeDate       SimpleDate
+		ExpectedPastDays int
+	}{
+		{
+			AfterDate:        mustParseSimpleDate("2023-01-01"),
+			BeforeDate:       mustParseSimpleDate("2022-12-31"),
+			ExpectedPastDays: 1,
+		},
+		{
+			AfterDate:        mustParseSimpleDate("2023-01-01"),
+			BeforeDate:       mustParseSimpleDate("2022-01-01"),
+			ExpectedPastDays: 365,
+		},
+	}
+
+	for i, tt := range tests {
+		if expected, got := tt.ExpectedPastDays, tt.AfterDate.CountPastDays(tt.BeforeDate); expected != got {
+			t.Fatalf("[%d] expected past days count: %d but got: %d", i, expected, got)
+		}
+	}
+}
+
+func mustParseSimpleDate(s string) SimpleDate {
+	d, err := ParseSimpleDate(s)
+	if err != nil {
+		panic(err)
+	}
+
+	return d
+}