JSON Date/Time Strings to Go time.Time

Converting JSON Date Strings to time.Time

Go's encoding/json package automatically parses RFC 3339 / ISO 8601 date strings into time.Time fields. This is the most common date format in JSON APIs.

Example JSON

{
  "id": 42,
  "title": "Deploy v2.0",
  "created_at": "2024-06-15T09:30:00Z",
  "updated_at": "2024-06-15T14:22:33+09:00",
  "due_date": "2024-07-01"
}

Generated Go Struct

import "time"

type Task struct {
    ID        int       `json:"id"`
    Title     string    `json:"title"`
    CreatedAt time.Time `json:"created_at"`
    UpdatedAt time.Time `json:"updated_at"`
    DueDate   string    `json:"due_date"`
}

What Parses Automatically

The time.Time type supports RFC 3339 out of the box:

• "2024-06-15T09:30:00Z" — UTC
• "2024-06-15T14:22:33+09:00" — with timezone offset

What Requires Custom Handling

Date-only strings like "2024-07-01" do not unmarshal into time.Time automatically. You have two options:

1. Keep it as string and parse manually with time.Parse("2006-01-02", s)
2. Create a custom type with UnmarshalJSON:

type DateOnly struct {
    time.Time
}

func (d *DateOnly) UnmarshalJSON(b []byte) error {
    s := strings.Trim(string(b), "\"")
    t, err := time.Parse("2006-01-02", s)
    if err != nil {
        return err
    }
    d.Time = t
    return nil
}

Timezone Awareness

time.Time preserves the timezone from the JSON string. CreatedAt.Location() returns UTC for "Z" suffixed timestamps. Always use .UTC() or .In(loc) for consistent comparisons.

Nullable Timestamps

Use *time.Time for timestamps that can be null:

DeletedAt *time.Time `json:"deleted_at,omitempty"`