Days between helper added. (#219)

# Describe Request

Days in between helper is added.

# Change Type

New feature.

helper/days_between.go

@@ -0,0 +1,15 @@
+// Copyright (c) 2021-2024 Onur Cinar.
+// The source code is provided under GNU AGPLv3 License.
+// https://github.com/cinar/indicator
+
+package helper
+
+import (
+	"math"
+	"time"
+)
+
+// DaysBetween calculates the days between the given two times.
+func DaysBetween(from, to time.Time) int {
+	return int(math.Floor(to.Sub(from).Hours() / 24))
+}

helper/days_between_test.go

@@ -0,0 +1,31 @@
+// Copyright (c) 2021-2024 Onur Cinar.
+// The source code is provided under GNU AGPLv3 License.
+// https://github.com/cinar/indicator
+
+package helper_test
+
+import (
+	"testing"
+	"time"
+
+	"github.com/cinar/indicator/v2/helper"
+)
+
+func TestDaysBetween(t *testing.T) {
+	from := time.Date(2024, 9, 1, 0, 0, 0, 0, time.UTC)
+	to := time.Date(2024, 9, 15, 0, 0, 0, 0, time.UTC)
+
+	actual := helper.DaysBetween(from, from)
+	expected := 0
+
+	if actual != expected {
+		t.Fatalf("actual %d expected %d", actual, expected)
+	}
+
+	actual = helper.DaysBetween(from, to)
+	expected = 14
+
+	if actual != expected {
+		t.Fatalf("actual %d expected %d", actual, expected)
+	}
+}