Use DateTime.Now.ToString("yyyy/MM/dd") 

https://docs.microsoft.com/en-us/dotnet/api/system.datetime.tostring?redirectedfrom=MSDN&view=netframework-4.8#System_DateTime_ToString_System_String_

using System;
					
public class Program
{
	public static void Main()
	{
		Console.WriteLine(DateTime.Now.ToString("yyyy/MM/dd"));
	}
}

//Output
2020/01/21