It would appear that my value is in seconds and not milliseconds.
Passing the value in milliseconds resolves the issue of rejection via the API.
Where as I appreciate the the idea of use of Unix time for specificity and formatting, when it comes to the fact that we have to communicate weather we are using Seconds or Milliseconds at that point have we not lost the universal nature of it? We now might as well use a date with a format.
“Unix time (also known as POSIX time or epoch time) is a system for describing instants in time, defined as the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970”
Epoch, also known as Unix timestamps, is the number of seconds (not milliseconds!)