time.Time.UnmarshalJSON() Function in Golang with Examples

In Go language, time packages supply the functionality for determining as well as viewing time. The UnmarshalJSON() function in Go language is used to implement the json.Unmarshaler interface. The time here is a quoted-string which is in RFC 3339 format. Moreover, this function is defined under the time package. Here, you need to import the “time” package in order to use these functions.

Syntax:

func (t *Time) UnmarshalJSON(data []byte) error

Here, “t” is the pointer to the stated time, and “data” is the byte slice that represents JSON’s encoding that was generated by MarshalJSON() method.

Return value: It decodes the encoding that was returned by MarshalJSON() method and returns an error occurred but if there is no error then “nil” is returned.

Example 1:

// Golang program to illustrate the usage of
// Time.UnmarshalJSON() function

// Including main package
package main

// Importing fmt and time
import "fmt"
import "time"

// Calling main
func main() {

    // Defining t for MarshalJSON method
    t := time.Date(2013, 7, 6, 12, 34, 33, 01, time.UTC)

    // Calling MarshalJSON() method
    encoding, _ := t.MarshalJSON()

    // Defining tm for UnmarshalJSON() method
    var tm time.Time

    // Calling UnmarshalJSON method with its parameters
    decode := tm.UnmarshalJSON(encoding)

    // Prints output
    fmt.Printf("Error: %v\n", decode)
}

Output:

Error: <nil>

Example 2:

// Golang program to illustrate the usage of
// Time.UnmarshalJSON() function

// Including main package
package main

// Importing fmt and time
import "fmt"
import "time"

// Calling main
func main() {

    // Defining t for MarshalJSON method
    t := time.Date(2034, 45, 33, 43, 90, 70, 6447, time.UTC)

    // Calling MarshalJSON() method
    encoding, _ := t.MarshalJSON()

    // Defining tm for UnmarshalJSON() method
    var tm time.Time

    // Calling UnmarshalJSON method with its parameters
    decode := tm.UnmarshalJSON(encoding)

    // Prints output
    fmt.Printf("Error: %v\n", decode)
}

Output:

Error: <nil>

Here, the “t” stated in the above code has values that are outside usual range but they are normalized while conversion.