using System;

​

public class Program

{

    public static void Main()

    {

        int nY, nMM, nD, nH, nM, nSec;

        DateTime yesterday = DateTime.Now.AddDays(-1);

        string test = "jacuzzis.dat.20191210090116";

        string[] testSplit = test.Split('.');

        string numString = testSplit[2];

        Int32.TryParse(numString.Substring(0, 4), out nY);

        Int32.TryParse(numString.Substring(4, 2), out nMM);

        Int32.TryParse(numString.Substring(6, 2), out nD);

        Int32.TryParse(numString.Substring(8, 2), out nH);

        Int32.TryParse(numString.Substring(10, 2), out nM);

        Int32.TryParse(numString.Substring(12, 2), out nSec);

        DateTime dateFromString = new DateTime(nY, nMM, nD, nH, nM, nSec);

        bool answer = false;        

        if(dateFromString.Date == yesterday.Date)       

        {answer = true;}

        Console.WriteLine("dateFromString = {0}\nToday={1}\nEval= {2}", dateFromString, yesterday, answer);

    }

}