如何从第二天开始获取特定时间？

Question

I want to create a time.Time for an exact point in time the following day (tomorrow). For now I would like to set the hour and minute.

This is the code I use at the moment:

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

This will create a Date for today with the exact time (hour and minute) I am looking for and then adds one day to that Date. This works fine.

---

Example:

Imagine time.Now() is 2009-11-10 23:00:00 +0000 UTC.

The result of the following code would be: 2009-11-10 15:00:00 +0000 UTC

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

To this date I add one day using AddDate(0, 0, 1). The result is then the desired time the next day: 2009-11-11 15:00:00 +0000 UTC.

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

---

Question:

Is there a shorter way to write this code?

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.

---

This is more efficient. It minimizes calls to package time functions and methods.

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)
}

Output:

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

---

Some benchmarks:

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
    }
}