using System;

using System.Globalization;

​

​

public class Program

{

    static public DateTime ParseDateTime(string input)

    {

        DateTime output;

        var ok = DateTime.TryParse(input, out output);

        if (ok) return output;

        return DateTime.Today;

    }

    static public TimeSpan ParseTime(string input)

    {

        DateTime output;

        var ok = DateTime.TryParseExact(input, @"h:mm tt", CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.NoCurrentDateDefault, out output);

        return output.Subtract(output.Date);

    }

    public static void Test1()

    {

        var dateEntered = @"08/03/2018";

        var timeEntered = @"3:00 am";

        DateTime result;

        var completeDateString = dateEntered + " " + timeEntered;

        var ok = DateTime.TryParse(completeDateString, out result);

        if (!ok) result = DateTime.Today;

        Console.WriteLine(result);

    }

    public static void Test2()

    {

        var dateEntered = @"08/03/2018";

        var timeEntered = @"3:00 am";

        DateTime dateResult = ParseDateTime(dateEntered);

        TimeSpan timeResult = ParseTime(timeEntered);

        DateTime finalResult = dateResult.Add(timeResult);

        Console.WriteLine(finalResult);

    }

    public static void Main()

    {

        Test1();

        Test2();

    }

}