Calculate number of days between two dates?

Question

How can I calculate the number of days between two dates? In the code below I should get the number of hours, which means that I should only need to divide by 24. However, the result I get is something like -44929.000000. I'm only looking a day or two back so I would expect 24 or 48 hours.

package main

import (
    "fmt"
    "time"
)

func main() {
    timeFormat := "2006-01-02"

    t, _ := time.Parse(timeFormat, "2014-12-28")
    fmt.Println(t)
    //  duration := time.Since(t)
    duration := time.Now().Sub(t)
    fmt.Printf("%f", duration.Hours())
}

Here's the executable Go code: http://play.golang.org/p/1MV6wnLVKh

Solution 1

Your program seems to work as intended. I'm getting 45.55 hours. Have you tried to run it locally?

Playground time is fixed, time.Now() will give you 2009-11-10 23:00:00 +0000 UTC always.

Solution 2

package main

import (
    "fmt"
    "time"
)

func main() {

    date := time.Now()
    fmt.Println(date)

    format := "2006-01-02 15:04:05"
    then,_ := time.Parse(format, "2007-09-18 11:58:06")
    fmt.Println(then)

    diff := date.Sub(then)

    //func Since(t Time) Duration
    //Since returns the time elapsed since t. 
    //It is shorthand for time.Now().Sub(t).

    fmt.Println(diff.Hours())// number of Hours
    fmt.Println(diff.Nanoseconds())// number of Nanoseconds
    fmt.Println(diff.Minutes())// number of Minutes
    fmt.Println(diff.Seconds())// number of Seconds

    fmt.Println(int(diff.Hours()/24))// number of days    

}

Here is the running code https://play.golang.org/p/Vbhh1cBKnh

Solution 3

the below code gives the list of all the days along with the number of days between the from date and to date: you can click on the link for the code in Go PlayGround:https://play.golang.org/p/MBThBpTqjdz

to := time.Now()
from := to.AddDate(0, -1, 0)
fmt.Println("toDate", to)
fmt.Println("fromDate", from)
days := to.Sub(from) / (24 * time.Hour)
fmt.Println("days", int(days))
noofdays := int(days)

for i := 0; i <= noofdays; i++ {
    fmt.Println(from.AddDate(0, 0, i))
}

Solution 4

One caveat to be mindful of when using this technique of timeOne.Sub(timeTwo).Hours() / 24 is that daylights savings can cause a day to contain only 23 hours, throwing this calculation off slightly.

View more solutions

Comments

[h4labs]

Ouch. I used to know that. I haven't used Go in a while. Thanks.

[Rick-777]

This still gives the wrong result when daylight savings changes happen. a Duration only represents the elapsed time between two instants as an int64 nanosecond count. It cannot be directly used to calculate days without errors twice a year. Sigh.

[Franva]

@Rick-777 do you have any solution for solving the issue you mentioned?

[Rick-777]

Yes, I worked on github.com/rickb777/date (forked from fxtlabs), which includes a Sub method. It uses the time api but works a bit harder to determine the dates of the two time instants before subtracting them.

[mikequentel]

int64(math.Ceil(duration.Hours() / 24)) is what I use to find number of days between two dates, where duration is the difference between two dates.