Opposite of Squirrel's date() function

I have a device which reports a timestamp to the imp. I am currently storing the timestamp in a table in the same format as what is returned from Squirrel’s date() function (without the wday and yday fields). To save on memory, I’d like to be able to store this value in an integer like what is returned from Squirrel’s time() function. date() allows you to go from integer->table but I don’t see a method to go from table->integer… Is this something that exists?