Problem to cronograph event using Time Library .

Hello everybody,
I’m working on a university project that involves using an Arduino Uno to get data from a pressure transducer. I need a program that records the times at two different value of pressure. Here the code I wrote:

#include <Time.h>

void setup() {
  // put your setup code here, to run once:,
Serial.begin(9600); //start talking with the computer. 9600 just tells the rate.

  setTime(12,05,55,01,12,2017);
}





void loop() {

  // put your main code here, to run repeatedly:

int sensorValue = analogRead(A0);

float Pressure =  sensorValue/5.637;

time_t t1=0;
time_t t2=0;
float Pstart;
float Pend;
int P1;
int P2;
int DeltaT;

P1=20;
P2=65;

if (Pressure<=P2+2){

Serial.println(Pressure);

if ((Pressure>=P1) && (Pressure<P1+1)){

t1=now();
Pstart=Pressure;

}

if ((Pressure>=P2) && (Pressure<P2+1)){

t2=now();
Pend=Pressure;
}

DeltaT=t2-t1;


}

else if (Pressure>P2+2)
{
Serial.println("DeltaT=");  
Serial.println(DeltaT);
Serial.println("P1=");
Serial.println(Pstart);
Serial.println("P2=");
Serial.println(Pend); 
}

  //exit(0);

 //delay (2000);

Basically the program reads the pressure until it reachs a specific value then it has to print the time passed between P1 and P2. The problem is that no matter what I do or change but the value DeltaT printed is always egual to zero.

I hope I wrote everything necessary to understand my problem. Thanks!

Your time_t variables should be static, as should your pressure variables.

AWOL:
Your time_t variables should be static, as should your pressure variables.

...or global

...or global and static 8)

AWOL:
Your time_t variables should be static, as should your pressure variables.

So you are suggesting either to change my variables inside the loop in "static time_t t1\ static float Pstart\ etc" or to put them outside the loop?

Yes.