go - 如何获取第二天的具体时间

Question

我想为第二天(明天)的确切时间点创建一个 time.Time。现在我想设置小时和分钟。

这是我目前使用的代码:

now := time.Now()
tomorrow := time.Date(now.Year(), now.Month(), now.Day(), 15, 0, 0, 0, time.UTC).AddDate(0,0,1)

这将为今天创建一个包含我正在寻找的确切时间(小时和分钟)的 Date，然后向该 Date 添加一天。这很好用。

---

示例:

假设 time.Now() 是 2009-11-10 23:00:00 +0000 UTC。

以下代码的结果为:2009-11-10 15:00:00 +0000 UTC

tomorrow := time.Date(now.Year(), now.Month(), now.Day(), 15, 0, 0, 0, time.UTC)

我使用 AddDate(0, 0, 1) 向这个日期添加了一天。结果就是第二天所需的时间:2009-11-11 15:00:00 +0000 UTC。

参见:https://play.golang.org/p/OKR9V1HN50x

---

问题:

有没有更短的方法来编写这段代码？

Answer 1

Package time

import "time" 

The month, day, hour, min, sec, and nsec values may be outside their usual ranges and will be normalized during the conversion. For example, October 32 converts to November 1.

---

这样效率更高。它最大限度地减少了对封装 time 函数和方法的调用。

package main

import (
    "fmt"
    "time"
)

func main() {
    now := time.Now()
    fmt.Println(now.Round(0))
    yyyy, mm, dd := now.Date()
    tomorrow := time.Date(yyyy, mm, dd+1, 15, 0, 0, 0, now.Location())
    fmt.Println(tomorrow)
}

输出:

2019-06-21 16:23:06.525478162 -0400 EDT
2019-06-22 15:00:00 -0400 EDT

---

一些基准:

BenchmarkNow-8                  31197811            36.6 ns/op
BenchmarkTomorrowPeterSO-8      29852671            38.4 ns/op
BenchmarkTomorrowJens-8          9523422           124 ns/op

bench_test.go:

package main

import (
    "testing"
    "time"
)

func BenchmarkNow(b *testing.B) {
    for N := 0; N < b.N; N++ {
        now := time.Now()
        _ = now
    }
}

var now = time.Now()

func BenchmarkTomorrowPeterSO(b *testing.B) {
    for N := 0; N < b.N; N++ {
        // now := time.Now()
        yyyy, mm, dd := now.Date()
        tomorrow := time.Date(yyyy, mm, dd+1, 15, 0, 0, 0, now.Location())
        _ = tomorrow
    }
}

func BenchmarkTomorrowJens(b *testing.B) {
    for N := 0; N < b.N; N++ {
        // now := time.Now()
        tomorrow := time.Date(now.Year(), now.Month(), now.Day(), 15, 0, 0, 0, now.Location()).AddDate(0, 0, 1)
        _ = tomorrow
    }
}