comment date format

src/main/kotlin/io/realworld/model/Comment.kt

@@ -5,7 +5,7 @@ import javax.persistence.*
 
 @Entity
 data class Comment(var createdAt: OffsetDateTime = OffsetDateTime.now(),
-                   var updatedAt: OffsetDateTime? = null,
+                   var updatedAt: OffsetDateTime = OffsetDateTime.now(),
                    var body: String = "",
                    @ManyToOne
                    var article: Article = Article(),

src/main/kotlin/io/realworld/model/inout/Comment.kt

@@ -2,21 +2,27 @@ package io.realworld.model.inout
 
 import com.fasterxml.jackson.annotation.JsonRootName
 import io.realworld.model.User
+import java.time.OffsetDateTime
+import java.time.ZoneId
 import java.time.format.DateTimeFormatter
 
 @JsonRootName("comment")
 data class Comment(val createdAt: String,
-                   val updatedAt: String?,
+                   val updatedAt: String,
                    val body: String,
                    val author: Profile,
                    val id: Long) {
     companion object {
+        fun dateFormat(date: OffsetDateTime): String {
+            return date.toZonedDateTime().withZoneSameInstant(ZoneId.of("Z")).format(DateTimeFormatter.ISO_ZONED_DATE_TIME)
+        }
+
         fun fromModel(model: io.realworld.model.Comment, currentUser: User): Comment {
             return Comment(
                     id = model.id,
                     body = model.body,
-                    createdAt = model.createdAt.format(DateTimeFormatter.ISO_DATE_TIME),
-                    updatedAt = model.updatedAt?.format(DateTimeFormatter.ISO_DATE_TIME),
+                    createdAt = dateFormat(model.createdAt),
+                    updatedAt = dateFormat(model.updatedAt),
                     author = Profile.fromUser(model.author, currentUser)
             )
         }