X-Gw-Timestamp request header contains the UNIX epoch (UTC) in milliseconds, such as
1648816933000. Some implementations of
strftime provide this as
%Q. In Ruby for example:
require 'date' timestamp = DateTime.now.strftime('%Q') request['X-Gw-Timestamp'] = timestamp
var timestamp = (new Date).getTime().toString();
If this is unavailable in your language or framework, multiplying the epoch by 1000 will be adequate.