using NodaTime;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            //Get now from system clock (this is an Instant)
            var now = SystemClock.Instance.Now;

            //get zoned datetime of now
            var ztNow = new ZonedDateTime(now, DateTimeZone.Utc);

            //now minus 8 months period converted to local datetime
            var  ltBeforePeriod = ztNow.LocalDateTime.Minus(Period.FromMonths(8));

            //Get zoned date time in utc
            var ztBeforePeriod = ltBeforePeriod.InUtc();

            //or convert it to your zone
            //ltAfterPeriod.InZoneStrictly(DateTimeZoneProviders.Tzdb.GetZoneOrNull("your zone id"));
        }
    }
}