From 9491b72b8dc44afb8ee96b64c69c9b7912fbb885 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mike=20Schw=C3=B6rer?= <pubgit@mikescher.com>
Date: Sat, 30 Mar 2024 03:01:55 +0100
Subject: [PATCH] v0.0.424 timeext.SubtractYears

---
 goextVersion.go |  4 ++--
 timeext/time.go | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/goextVersion.go b/goextVersion.go
index 2e89a07..3522582 100644
--- a/goextVersion.go
+++ b/goextVersion.go
@@ -1,5 +1,5 @@
 package goext
 
-const GoextVersion = "0.0.423"
+const GoextVersion = "0.0.424"
 
-const GoextVersionTimestamp = "2024-03-24T15:25:52+0100"
+const GoextVersionTimestamp = "2024-03-30T03:01:55+0100"
diff --git a/timeext/time.go b/timeext/time.go
index 34b2a70..4af8ac1 100644
--- a/timeext/time.go
+++ b/timeext/time.go
@@ -146,3 +146,37 @@ func UnixFloatSeconds(v float64) time.Time {
 func FloorTime(t time.Time) time.Time {
 	return time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, t.Location())
 }
+
+func SubtractYears(t time.Time, yearCount float64, tz *time.Location) time.Time {
+	t = t.In(tz)
+
+	if yearCount < 0 {
+		return AddYears(t, -yearCount, tz)
+	}
+
+	intCount, floatCount := math.Modf(yearCount)
+
+	t.AddDate(-int(intCount), 0, 0)
+
+	t0 := TimeToYearStart(t, tz)
+	t1 := TimeToYearEnd(t, tz)
+
+	return t.Add(time.Duration(float64(t1.Sub(t0)) * floatCount * -1))
+}
+
+func AddYears(t time.Time, yearCount float64, tz *time.Location) time.Time {
+	t = t.In(tz)
+
+	if yearCount < 0 {
+		return SubtractYears(t, -yearCount, tz)
+	}
+
+	intCount, floatCount := math.Modf(yearCount)
+
+	t.AddDate(int(intCount), 0, 0)
+
+	t0 := TimeToYearStart(t, tz)
+	t1 := TimeToYearEnd(t, tz)
+
+	return t.Add(time.Duration(float64(t1.Sub(t0)) * floatCount))
+}