diff --git a/operator-and-conversation/go/seats/operatorchannel/contract.go b/operator-and-conversation/go/seats/operatorchannel/contract.go
index 6d30be7..8fb2a22 100644
--- a/operator-and-conversation/go/seats/operatorchannel/contract.go
+++ b/operator-and-conversation/go/seats/operatorchannel/contract.go
@@ -8,6 +8,7 @@ import (
 	"encoding/json"
 	"errors"
 	"strings"
+	"time"
 )
 
 // Seat is the seat's name.
@@ -160,7 +161,7 @@ type Button struct {
 // Choice is a button chosen on a channel, said on the bench intake as the event `choice`.
 type Choice struct {
 	// when, RFC 3339
-	At string `json:"at"`
+	At time.Time `json:"at"`
 	// the message's handle
 	Handle string `json:"handle,omitempty"`
 	// the channel's own for this arrival, unique, so the router acts on it once
@@ -230,7 +231,7 @@ type Condition struct {
 // Failed is a message a channel could not deliver, said on the bench intake as the event `failed`.
 type Failed struct {
 	// when, RFC 3339
-	At string `json:"at"`
+	At time.Time `json:"at"`
 	// the message's handle
 	Handle string `json:"handle"`
 	// trying again cannot help
@@ -242,7 +243,7 @@ type Failed struct {
 // LinkAsked is somebody on a channel asking to be linked as the operator, said on the bench intake as the event `link`.
 type LinkAsked struct {
 	// when, RFC 3339
-	At string `json:"at"`
+	At time.Time `json:"at"`
 	// the channel's own for this arrival
 	ID     string `json:"id"`
 	Sender Sender `json:"sender"`
@@ -321,7 +322,7 @@ type Sender struct {
 // Standing is what a channel says of itself at least every five minutes and whenever it changes, on the bench intake as the event `standing`.
 type Standing struct {
 	// when, RFC 3339
-	At string `json:"at"`
+	At time.Time `json:"at"`
 	// its edits notify nobody
 	EditsSilently bool `json:"edits-silently,omitempty"`
 	// it can send now
diff --git a/operator-and-conversation/seats/operator-channel/seat.json b/operator-and-conversation/seats/operator-channel/seat.json
index a9a5365..3f33532 100644
--- a/operator-and-conversation/seats/operator-channel/seat.json
+++ b/operator-and-conversation/seats/operator-channel/seat.json
@@ -728,7 +728,8 @@
         },
         "at": {
           "type": "string",
-          "description": "when, RFC 3339"
+          "description": "when, RFC 3339",
+          "format": "date-time"
         }
       },
       "required": [
@@ -751,7 +752,8 @@
         },
         "at": {
           "type": "string",
-          "description": "when, RFC 3339"
+          "description": "when, RFC 3339",
+          "format": "date-time"
         }
       },
       "required": [
@@ -778,7 +780,8 @@
         },
         "at": {
           "type": "string",
-          "description": "when, RFC 3339"
+          "description": "when, RFC 3339",
+          "format": "date-time"
         }
       },
       "required": [
@@ -805,7 +808,8 @@
         },
         "at": {
           "type": "string",
-          "description": "when, RFC 3339"
+          "description": "when, RFC 3339",
+          "format": "date-time"
         }
       },
       "required": [