xamarin 12 hrs time format tt

public static class MyExtensionClass
{
    public static string ToFormat12h(this DateTime dt)
    {
        return dt.ToString("yyyy/MM/dd, hh:mm:ss tt");
    }

    public static string ToFormat24h(this DateTime dt)
    {
        return dt.ToString("yyyy/MM/dd, HH:mm:ss");
    }
}