DD.WellWorkover.Cloud/ConsoleApp1/Cron.cs

using System;

namespace ConsoleApp1
{
    class Cron
    {
        public DateTimeOffset Origin { get; set; }
        public TimeSpan Period { get; set; }

        public DateTimeOffset Next()
        {
            var delta = DateTimeOffset.Now - Origin;
            var n = Math.Ceiling(delta / Period);
            return Origin + n * Period;
        }
    }
}