diff --git a/data/generators.go b/data/generators.go
index 95e73f4..7cfe124 100644
--- a/data/generators.go
+++ b/data/generators.go
@@ -336,7 +336,7 @@ func GenerateRandomConversation() model.Conversation {
 		Participants: []string{GenerateRandomName()},
 		UnreadCount:  0,
 		Guid:         uuid.New().String(),
-		Date:         time.Now().Add(-1 * time.Duration(rand.Intn(1000000)) * time.Second),
+		Date:         model.Date(time.Now().Add(-1 * time.Duration(rand.Intn(1000000)) * time.Second)),
 	}
 
 	return conversation
@@ -355,7 +355,7 @@ func GenerateRandomMessage(participants []string) model.Message {
 	return model.Message{
 		Text:   GenerateRandomMessageBody(),
 		Guid:   uuid.New().String(),
-		Date:   time.Now().Add(-1 * time.Duration(rand.Intn(1000000)) * time.Second),
+		Date:   model.Date(time.Now().Add(-1 * time.Duration(rand.Intn(1000000)) * time.Second)),
 		Sender: sender,
 	}
 }
diff --git a/model/authtoken.go b/model/authtoken.go
index 264d798..75dd6c1 100644
--- a/model/authtoken.go
+++ b/model/authtoken.go
@@ -4,8 +4,8 @@ import (
 	"encoding/base64"
 	"time"
 
-    "github.com/rs/zerolog/log"
 	"github.com/dgrijalva/jwt-go"
+	"github.com/rs/zerolog/log"
 )
 
 type AuthToken struct {
diff --git a/model/conversation.go b/model/conversation.go
index a23531b..549bebe 100644
--- a/model/conversation.go
+++ b/model/conversation.go
@@ -8,13 +8,13 @@ import (
 )
 
 type Conversation struct {
-	Date               time.Time `json:"date"`
-	Participants       []string  `json:"participantDisplayNames"`
-	DisplayName        *string   `json:"displayName,omitempty"` // Optional
-	UnreadCount        int       `json:"unreadCount"`
-	LastMessagePreview string    `json:"lastMessagePreview"`
-	LastMessage        Message   `json:"lastMessage"`
-	Guid               string    `json:"guid"`
+	Date               Date     `json:"date"`
+	Participants       []string `json:"participantDisplayNames"`
+	DisplayName        *string  `json:"displayName,omitempty"` // Optional
+	UnreadCount        int      `json:"unreadCount"`
+	LastMessagePreview string   `json:"lastMessagePreview"`
+	LastMessage        Message  `json:"lastMessage"`
+	Guid               string   `json:"guid"`
 }
 
 func (c *Conversation) GetDisplayName() string {
@@ -27,7 +27,7 @@ func (c *Conversation) GetDisplayName() string {
 
 func (c *Conversation) MarshalZerologObject(e *zerolog.Event) {
 	e.Str("guid", c.Guid)
-	e.Time("date", c.Date)
+	e.Time("date", time.Time(c.Date))
 	e.Int("unreadCount", c.UnreadCount)
 	e.Str("lastMessagePreview", c.LastMessagePreview)
 	e.Strs("participants", c.Participants)
diff --git a/model/date.go b/model/date.go
new file mode 100644
index 0000000..552e20e
--- /dev/null
+++ b/model/date.go
@@ -0,0 +1,30 @@
+package model
+
+import (
+	"fmt"
+	"time"
+)
+
+type Date time.Time
+
+func (d Date) Equal(other Date) bool {
+	return time.Time(d).Equal(time.Time(other))
+}
+
+func (d Date) After(other Date) bool {
+	return time.Time(d).After(time.Time(other))
+}
+
+func (d Date) Before(other Date) bool {
+	return time.Time(d).Before(time.Time(other))
+}
+
+func (d Date) Format(layout string) string {
+	return time.Time(d).Format(layout)
+}
+
+func (t Date) MarshalJSON() ([]byte, error) {
+	// Must use ISO8601
+	formatted := fmt.Sprintf("\"%s\"", time.Time(t).Format("2006-01-02T15:04:05+00:00"))
+	return []byte(formatted), nil
+}
diff --git a/model/message.go b/model/message.go
index c173abd..d88768a 100644
--- a/model/message.go
+++ b/model/message.go
@@ -1,16 +1,15 @@
 package model
 
 import (
-	"time"
-
 	"github.com/rs/zerolog"
+	"time"
 )
 
 type Message struct {
-	Text   string    `json:"text"`
-	Guid   string    `json:"guid"`
-	Sender *string   `json:"sender,omitempty"` // Optional: nil means from "me"
-	Date   time.Time `json:"date"`
+	Text   string  `json:"text"`
+	Guid   string  `json:"guid"`
+	Sender *string `json:"sender,omitempty"` // Optional: nil means from "me"
+	Date   Date    `json:"date"`
 
 	// Map of attachment GUID to attachment metadata
 	Attachments *map[string]AttributionInfo `json:"attachmentMetadata,omitempty"` // Optional
@@ -24,7 +23,7 @@ type AttributionInfo struct {
 func (c Message) MarshalZerologObject(e *zerolog.Event) {
 	e.Str("guid", c.Guid)
 	e.Str("text", c.Text)
-	e.Time("date", c.Date)
+	e.Time("date", time.Time(c.Date))
 
 	if c.Sender != nil {
 		e.Str("sender", *c.Sender)
diff --git a/prompt/prompt.go b/prompt/prompt.go
index ff88239..0e7959f 100644
--- a/prompt/prompt.go
+++ b/prompt/prompt.go
@@ -85,7 +85,7 @@ func (p *Prompt) receiveMessage(guid string, text string) {
 		Guid:   uuid.New().String(),
 		Sender: &conversation.Participants[0],
 		Text:   text,
-		Date:   time.Now(),
+		Date:   model.Date(time.Now()),
 	}
 
 	p.server.ReceiveMessage(conversation, message)
diff --git a/server/server.go b/server/server.go
index 0340a54..b49c9f0 100644
--- a/server/server.go
+++ b/server/server.go
@@ -2,7 +2,6 @@ package server
 
 import (
 	"sort"
-	"time"
 
 	"code.severnaya.net/kordophone-mock/v2/data"
 	"code.severnaya.net/kordophone-mock/v2/model"
@@ -28,7 +27,7 @@ type Server struct {
 
 type MessagesQuery struct {
 	ConversationGUID string
-	BeforeDate       *time.Time
+	BeforeDate       *model.Date
 	AfterGUID        *string
 	BeforeGUID       *string
 	Limit            *int
diff --git a/web/server.go b/web/server.go
index 344e33e..b926513 100644
--- a/web/server.go
+++ b/web/server.go
@@ -139,12 +139,13 @@ func (m *MockHTTPServer) handleMessages(w http.ResponseWriter, r *http.Request)
 		return &s
 	}
 
-	dateOrNil := func(s string) *time.Time {
+	dateOrNil := func(s string) *model.Date {
 		if len(s) == 0 {
 			return nil
 		}
 		t, _ := time.Parse(time.RFC3339, s)
-		return &t
+		date := model.Date(t)
+		return &date
 	}
 
 	intOrNil := func(s string) *int {
@@ -241,7 +242,7 @@ func (m *MockHTTPServer) handleSendMessage(w http.ResponseWriter, r *http.Reques
 	message := model.Message{
 		Guid:   uuid.New().String(),
 		Text:   sendMessageReq.Body,
-		Date:   time.Now(),
+		Date:   model.Date(time.Now()),
 		Sender: nil, // me
 	}