v0.0.509

goextVersion.go

@@ -1,5 +1,5 @@
 package goext
 
-const GoextVersion = "0.0.508"
+const GoextVersion = "0.0.509"
 
-const GoextVersionTimestamp = "2024-08-25T17:36:20+0200"
+const GoextVersionTimestamp = "2024-08-26T14:35:49+0200"

timeext/diff.go

@@ -2,6 +2,9 @@ package timeext
 
 import "time"
 
+// YearDifference calculates the difference between two timestamps in years.
+// = t1 - t2
+// returns a float value
 func YearDifference(t1 time.Time, t2 time.Time, tz *time.Location) float64 {
 
 	yDelta := float64(t1.Year() - t2.Year())
@@ -11,3 +14,31 @@ func YearDifference(t1 time.Time, t2 time.Time, tz *time.Location) float64 {
 
 	return yDelta + (processT1 - processT2)
 }
+
+// MonthDifference calculates the difference between two timestamps in months.
+// = t1 - t2
+// returns a float value
+func MonthDifference(t1 time.Time, t2 time.Time) float64 {
+
+	yDelta := float64(t1.Year() - t2.Year())
+	mDelta := float64(t1.Month() - t2.Month())
+
+	dDelta := float64(0)
+
+	t1MonthDays := DaysInMonth(t1)
+	t2MonthDays := DaysInMonth(t2)
+
+	if t2.Year() > t1.Year() || (t2.Year() == t1.Year() && t2.Month() > t1.Month()) {
+		dDelta -= 1
+		dDelta += float64(t1MonthDays-t1.Day()) / float64(t1MonthDays)
+		dDelta += float64(t2.Day()) / float64(t2MonthDays)
+	} else if t2.Year() < t1.Year() || (t2.Year() == t1.Year() && t2.Month() < t1.Month()) {
+		dDelta -= 1
+		dDelta += float64(t1.Day()) / float64(t1MonthDays)
+		dDelta += float64(t2MonthDays-t2.Day()) / float64(t2MonthDays)
+	} else {
+		dDelta += float64(t1.Day()-t2.Day()) / float64(t1MonthDays)
+	}
+
+	return yDelta*12 + mDelta + dDelta
+}

timeext/diff_test.go

@@ -81,3 +81,63 @@ func epsilonEquals(a, b float64) bool {
 	epsilon := 0.01
 	return math.Abs(a-b) < epsilon
 }
+
+func TestMonthDifferenceSameDate(t *testing.T) {
+	t1 := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
+	t2 := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
+	expected := 0.0
+	result := MonthDifference(t2, t1)
+	if !epsilonEquals(result, expected) {
+		t.Errorf("Expected %v, got %v", expected, result)
+	}
+}
+
+func TestMonthDifferenceSameMonth(t *testing.T) {
+	t1 := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
+	t2 := time.Date(2022, 1, 31, 0, 0, 0, 0, time.UTC)
+	expected := 0.967741935483871 // Approximation of 30/31 days
+	result := MonthDifference(t2, t1)
+	if !epsilonEquals(result, expected) {
+		t.Errorf("Expected %v, got %v", expected, result)
+	}
+}
+
+func TestMonthDifferenceDifferentMonthsSameYear(t *testing.T) {
+	t1 := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
+	t2 := time.Date(2022, 3, 1, 0, 0, 0, 0, time.UTC)
+	expected := 2.0
+	result := MonthDifference(t2, t1)
+	if !epsilonEquals(result, expected) {
+		t.Errorf("Expected %v, got %v", expected, result)
+	}
+}
+
+func TestMonthDifferenceDifferentYears(t *testing.T) {
+	t1 := time.Date(2021, 12, 1, 0, 0, 0, 0, time.UTC)
+	t2 := time.Date(2022, 2, 1, 0, 0, 0, 0, time.UTC)
+	expected := 2.0
+	result := MonthDifference(t2, t1)
+	if !epsilonEquals(result, expected) {
+		t.Errorf("Expected %v, got %v", expected, result)
+	}
+}
+
+func TestMonthDifferenceT1BeforeT2(t *testing.T) {
+	t1 := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
+	t2 := time.Date(2022, 6, 1, 0, 0, 0, 0, time.UTC)
+	expected := 5.0
+	result := MonthDifference(t2, t1)
+	if !epsilonEquals(result, expected) {
+		t.Errorf("Expected %v, got %v", expected, result)
+	}
+}
+
+func TestMonthDifferenceT1AfterT2(t *testing.T) {
+	t1 := time.Date(2022, 6, 1, 0, 0, 0, 0, time.UTC)
+	t2 := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
+	expected := -5.0
+	result := MonthDifference(t2, t1)
+	if !epsilonEquals(result, expected) {
+		t.Errorf("Expected %v, got %v", expected, result)
+	}
+}

timeext/time.go

@@ -184,3 +184,10 @@ func AddYears(t time.Time, yearCount float64, tz *time.Location) time.Time {
 
 	return t.Add(time.Duration(float64(t1.Sub(t0)) * floatCount))
 }
+
+func DaysInMonth(t time.Time) int {
+	// https://stackoverflow.com/a/73882035/1761622
+
+	y, m, _ := t.Date()
+	return time.Date(y, m+1, 0, 0, 0, 0, 0, time.UTC).Day()
+}

timeext/time_test.go

@@ -191,3 +191,39 @@ func TestCombineDateAndTime_CombineDifferentParts(t *testing.T) {
 		t.Errorf("Expected %v, got %v", expected, result)
 	}
 }
+
+func TestDaysInMonth_31Days(t *testing.T) {
+	date := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC) // January
+	expected := 31
+	result := DaysInMonth(date)
+	if result != expected {
+		t.Errorf("Expected %d but got %d", expected, result)
+	}
+}
+
+func TestDaysInMonth_30Days(t *testing.T) {
+	date := time.Date(2022, 4, 1, 0, 0, 0, 0, time.UTC) // April
+	expected := 30
+	result := DaysInMonth(date)
+	if result != expected {
+		t.Errorf("Expected %d but got %d", expected, result)
+	}
+}
+
+func TestDaysInMonth_FebruaryLeapYear(t *testing.T) {
+	date := time.Date(2020, 2, 1, 0, 0, 0, 0, time.UTC) // February in a leap year
+	expected := 29
+	result := DaysInMonth(date)
+	if result != expected {
+		t.Errorf("Expected %d but got %d", expected, result)
+	}
+}
+
+func TestDaysInMonth_FebruaryNonLeapYear(t *testing.T) {
+	date := time.Date(2021, 2, 1, 0, 0, 0, 0, time.UTC) // February in a non-leap year
+	expected := 28
+	result := DaysInMonth(date)
+	if result != expected {
+		t.Errorf("Expected %d but got %d", expected, result)
+	}
+}