昨日、○日前、○週間前、○月前、明日、○週間後、○日後、○ヶ月後などを取得する(time.AddDate)

Golang

pv:

前系

time.AddDate(years, months, days) -1を渡すと前の日にも戻れる

// 昨日
t1 := time.Date(2019, 12, 1, 23, 59, 59, 999999999, time.UTC)
fmt.Println(t1.AddDate(0, 0, -1))
// ちゃんと月をまたげる
// => 2019-11-30 23:59:59.999999999 +0000 UTC

// 10日前
t2 := time.Date(2019, 12, 1, 23, 59, 59, 999999999, time.UTC)
fmt.Println(t2.AddDate(0, 0, -10))
// => 2019-11-21 23:59:59.999999999 +0000 UTC

// 1週間前
t3 := time.Date(2019, 12, 1, 23, 59, 59, 999999999, time.UTC)
fmt.Println(t3.AddDate(0, 0, -7))
// => 2019-11-24 23:59:59.999999999 +0000 UTC

// 1ヶ月前
t4 := time.Date(2019, 12, 31, 23, 59, 59, 999999999, time.UTC)
fmt.Println(t4.AddDate(0, -1, 0))
// => 2019-12-01 23:59:59.999999999 +0000 UTC
// 30日を引いてるだけに見える

後系

// 明日
t5 := time.Date(2019, 12, 31, 23, 59, 59, 999999999, time.UTC)
fmt.Println(t5.AddDate(0, 0, 1))
// => 2020-01-01 23:59:59.999999999 +0000 UTC

// 10日後
t6 := time.Date(2019, 12, 31, 23, 59, 59, 999999999, time.UTC)
fmt.Println(t6.AddDate(0, 0, 10))
// => 2020-01-10 23:59:59.999999999 +0000 UTC

// 1週間後
t7 := time.Date(2019, 12, 31, 23, 59, 59, 999999999, time.UTC)
fmt.Println(t7.AddDate(0,0,7))
// => 2020-01-07 23:59:59.999999999 +0000 UTC

// 1ヶ月後
t8 := time.Date(2019, 12, 31, 23, 59, 59, 999999999, time.UTC)
fmt.Println(t8.AddDate(0,1,0))
// => 2020-01-31 23:59:59.999999999 +0000 UTC

コピペ実行用

package main

import (
	"fmt"
	"time"
)

//--------------------------------------------------------
// 昨日、○日前、○週間前、○月前、明日、○週間後、○日後、○ヶ月後などを取得する(time.AddDate)
//--------------------------------------------------------

func main() {
	// 前系
	
	// time.AddDate(years, months, days)
	// -1を渡すと前の日にも戻れる
	
	// 昨日
	t1 := time.Date(2019, 12, 1, 23, 59, 59, 999999999, time.UTC)
	fmt.Println(t1.AddDate(0, 0, -1))
	// ちゃんと月をまたげる
	// => 2019-11-30 23:59:59.999999999 +0000 UTC

	// 10日前
	t2 := time.Date(2019, 12, 1, 23, 59, 59, 999999999, time.UTC)
	fmt.Println(t2.AddDate(0, 0, -10))
	// => 2019-11-21 23:59:59.999999999 +0000 UTC

	// 1週間前
	t3 := time.Date(2019, 12, 1, 23, 59, 59, 999999999, time.UTC)
	fmt.Println(t3.AddDate(0, 0, -7))
	// => 2019-11-24 23:59:59.999999999 +0000 UTC

	// 1ヶ月前
	t4 := time.Date(2019, 12, 31, 23, 59, 59, 999999999, time.UTC)
	fmt.Println(t4.AddDate(0, -1, 0))
	// => 2019-12-01 23:59:59.999999999 +0000 UTC
	// 30日を引いてるだけに見える

	// 後系

	// 明日
	t5 := time.Date(2019, 12, 31, 23, 59, 59, 999999999, time.UTC)
	fmt.Println(t5.AddDate(0, 0, 1))
	// => 2020-01-01 23:59:59.999999999 +0000 UTC

	// 10日後
	t6 := time.Date(2019, 12, 31, 23, 59, 59, 999999999, time.UTC)
	fmt.Println(t6.AddDate(0, 0, 10))
	// => 2020-01-10 23:59:59.999999999 +0000 UTC

	// 1週間後
	t7 := time.Date(2019, 12, 31, 23, 59, 59, 999999999, time.UTC)
	fmt.Println(t7.AddDate(0,0,7))
	// => 2020-01-07 23:59:59.999999999 +0000 UTC

	// 1ヶ月後
	t8 := time.Date(2019, 12, 31, 23, 59, 59, 999999999, time.UTC)
	fmt.Println(t8.AddDate(0,1,0))
	// => 2020-01-31 23:59:59.999999999 +0000 UTC
}