ScheduledTaskManager.Task.cs

public class Task
{
    // Action based :D
    public Action Action { get; set; }

    public int? AbsoluteMinute { get; set; }
    public int? AbsoluteHour { get; set; }

    public int? SlidingMinute { get; set; }
    public int? SlidingHour { get; set; }

    private bool IsAbsolute { get { return AbsoluteMinute.HasValue; } }
    private bool IsSliding { get { return SlidingMinute.HasValue; } }

    private Func<DateTime> Watch;
    public Task(Func<DateTime> currentTimeWatch = null)
    {
        this.Watch = currentTimeWatch ?? new Func<DateTime>(Helper.GetCurrentDatetime);
    }
        
    private DateTime last;
    public bool IsTime()
    {
        var now = Normalize(Watch());
        if (last == default(DateTime))
            last = now;

        bool risp = false;

        if (IsAbsolute)
        {
            var absoluteTime = new DateTime(now.Year, now.Month, now.Day, AbsoluteHour.HasValue ? AbsoluteHour.Value : now.Hour, AbsoluteMinute.Value, 0);
            risp = last < absoluteTime && absoluteTime <= now;
        }
        else if (IsSliding)
        {
            var minutes = (SlidingHour.HasValue ? SlidingHour.Value * 60 : 0) + SlidingMinute.Value;
            risp = (now - last).TotalMinutes >= minutes;
        }

        if (risp)
            last = now;

        return risp;
    }

    private DateTime Normalize(DateTime arg)
    {
        return new DateTime(arg.Year, arg.Month, arg.Day, arg.Hour, arg.Minute, arg.Second);
    }
}

// Helper Class
public static class Helper
{
    public static DateTime GetCurrentDatetime() 
    {
        // real datetime or custom system's datetime
        return DateTime.Now;    
    }
}