diff --git a/src/engine/rfc822/rfc822-message-data.vala b/src/engine/rfc822/rfc822-message-data.vala
index 8c9cdb40..975fc7e1 100644
--- a/src/engine/rfc822/rfc822-message-data.vala
+++ b/src/engine/rfc822/rfc822-message-data.vala
@@ -164,7 +164,11 @@ public class Geary.RFC822.Date : Geary.RFC822.MessageData, Geary.MessageData.Abs
      * Returns the {@link Date} in ISO-8601 format.
      */
     public virtual string serialize() {
-        return GMime.utils_header_format_date(as_time_t, 0);
+        // Although GMime documents its conversion methods as requiring the tz offset in hours,
+        // it appears the number is handed directly to the string (i.e. an offset of -7 becomes
+        // "-0007", whereas we want "-0700").
+        return GMime.utils_header_format_date(as_time_t,
+            (int) (value.get_utc_offset() / TimeSpan.HOUR) * 100);
     }
     
     public virtual uint hash() {
diff --git a/src/engine/rfc822/rfc822-message.vala b/src/engine/rfc822/rfc822-message.vala
index aa32c6bf..f38b6942 100644
--- a/src/engine/rfc822/rfc822-message.vala
+++ b/src/engine/rfc822/rfc822-message.vala
@@ -96,8 +96,7 @@ public class Geary.RFC822.Message : BaseObject {
         date = new RFC822.Date.from_date_time(email.date);
         
         message.set_sender(sender.to_rfc822_string());
-        message.set_date((time_t) email.date.to_unix(),
-            (int) (email.date.get_utc_offset() / TimeSpan.HOUR));
+        message.set_date_as_string(date.serialize());
         if (message_id != null)
             message.set_message_id(message_id);