I have a specific problem I've been trying to solve, and I think I have the right pieces - I'm just putting them together incorrectly. It might be more of a math question than a coding one.

So basically what I want to be able to do is find where "now" is within an arbitrary recurring time period (say, 43 minutes), given a known DateTime that this period recurred. So you have an anchor point, and from that anchor point, you know that every 43 minutes this period starts over, where is "now" in the current period?

I'm sure it involves division and/or modulo, and likely a subtraction using the anchor...so I've been toying with this code, but it isn't giving me the results I'm looking for:

```
using System;

public class Program
{
    public static void Main()
    {
        TimeSpan interval = new TimeSpan(0, 43, 0);
        DateTime anchor = new DateTime(2018, 1, 5, 7, 0, 49);
        DateTime now = DateTime.Now;

        TimeSpan left = new TimeSpan((now - anchor).Ticks % interval.Ticks);

        Console.WriteLine(left);
    }
}

```

Can someone tell me the piece I'm missing here? I'm not entirely sure what mathematical operations DateTime supports, or which ones I should be using in this instance.

Thanks.