FYI: since you are already using TimeLib.h, here is how to get a unix time stamp from an arbitrary date:
#include "TimeLib.h"
tmElements_t te; //Time elements structure
time_t unixTime; // a time stamp
void setup() {
Serial.begin(9600);
// convert an arbitrary date and time into a unix timestamp (since 1970)
te.Second = 0;
te.Hour = 0;
te.Minute = 0;
te.Day = 1; //start date: Jan 1, 2000
te.Month = 1;
te.Year = 2000-1970; //Y2K, in seconds should be 946684800UL
unixTime = makeTime(te);
Serial.print("unixTime = ");
Serial.println(unixTime);
Serial.print("now() = ");
Serial.println((unsigned long) now());
}
void loop() {}