如何在Go中表示RFC-3339`-00：00`偏移量？

Question

RFC-3339 Section 4.3 (https://tools.ietf.org/html/rfc3339#section-4.3) defines the -00:00 offset as the following, which is different than Z or +00:00.

4.3. Unknown Local Offset Convention

   If the time in UTC is known, but the offset to local time is unknown,
   this can be represented with an offset of "-00:00".  This differs
   semantically from an offset of "Z" or "+00:00", which imply that UTC
   is the preferred reference point for the specified time.  RFC2822
   [IMAIL-UPDATE] describes a similar convention for email.

However, I'm not sure how to represent this in Go. When I parse a time with -00:00 and format it, I get a Z offset. For example:

• Input: 2018-01-01T00:00:00-00:00
• Output: 2018-01-01T00:00:00Z

Here's some example code (https://play.golang.org/p/CVmNnhaSiiT):

package main

import (
    "fmt"
    "time"
)

func main() {
    t := "2018-01-01T00:00:00-00:00"
    fmt.Println("Input  " + t)
    p, err := time.Parse(time.RFC3339, t)
    if err != nil {
        fmt.Println(err)
    } else {
        t2 := p.Format(time.RFC3339)

        fmt.Println("Output " + t2)
    }
}

Answer 1

Package time

import "time"

RFC3339, RFC822, RFC822Z, RFC1123, and RFC1123Z are useful for formatting; when used with time.Parse they do not accept all the time formats permitted by the RFCs.

---

Go does not accept all the time formats permitted by the RFCs.

The Go time.Time type uses integers which, unlike floating-point, have no concept of plus and minus zero. The results for parsing offsets of -00:00 and +00:00 are identical.

For example,

package main

import (
    "fmt"
    "time"
)

func main() {
    var err error
    var minus, plus time.Time
    t := "2018-01-01T00:00:00-00:00"
    minus, err = time.Parse(time.RFC3339, t)
    if err != nil {
        fmt.Println(err)
    }
    t = "2018-01-01T00:00:00+00:00"
    plus, err = time.Parse(time.RFC3339, t)
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println(minus, plus, minus.Equal(plus), minus == plus)
}

Playground: https://play.golang.org/p/Urf8VlKYoMH

Output:

2018-01-01 00:00:00 +0000 UTC 2018-01-01 00:00:00 +0000 UTC true true