Datetime and offsets in .net

Question

How can I schedule a background job to start every day at 9pm in Colombian time? Im using quartz.net

public class Program
    {
        static void Main(string[] args)
        {
            // construct a scheduler

            var schedulerFactory = new StdSchedulerFactory();
            var scheduler = schedulerFactory.GetScheduler();
            scheduler.Start();


            TimeZoneInfo colombianTimezone = TimeZoneInfo.FindSystemTimeZoneById("SA Pacific Standard Time");     
            var colombianTimeNow = TimeZoneInfo.ConvertTime(DateTime.Now, TimeZoneInfo.Local,
                                                            colombianTimezone);    

            var job = JobBuilder.Create<EmailsJob>().Build();
            var now = DateTime.Now;

            var trigger = TriggerBuilder.Create()
                            .StartAt(//INeedThisToStartEverydayat9pmColombianTime)
                            .WithSimpleSchedule(x => x.WithIntervalInHours(24).RepeatForever())
                            .Build();

            scheduler.ScheduleJob(job, trigger);
        }
    }

The StartAt method takes a DateTimeOffset object.

Please help

Answer 1

Cron based scheduling might be better alternative for your needs.

TimeZoneInfo colombianTimezone = TimeZoneInfo.FindSystemTimeZoneById("SA Pacific Standard Time");     

var job = JobBuilder.Create<EmailsJob>().Build();

var trigger = TriggerBuilder.Create()
                .WithCronSchedule("0 0 21 * * ?", x => x.InTimeZone(colombianTimezone))
                .Build();

scheduler.ScheduleJob(job, trigger);

Answer 2

This should give you a DateTimeOffset for today at 9pm, converted to UniversalTime to pass to quartz.

TimeZoneInfo colombianTimezone = TimeZoneInfo.FindSystemTimeZoneById("SA Pacific Standard Time");
DateTime columbianTime9pm = TimeZoneInfo.ConvertTime(DateTime.Today.AddHours(21), TimeZoneInfo.Local,
                                                colombianTimezone);
DateTimeOffset startAt = new DateTimeOffset(columbianTime9pm).ToUniversalTime();

I haven't tested it, but I think this will also define the trigger you want.

TimeZoneInfo colombianTimezone = TimeZoneInfo.FindSystemTimeZoneById("SA Pacific Standard Time");
DateTime startTime = TimeZoneInfo.ConvertTime(DateTime.Today.AddHours(21), TimeZoneInfo.Local,
                                                colombianTimezone);
SimpleTrigger trigger = new SimpleTrigger("myTrigger",
                                            null,
                                            startTime,
                                            null,
                                            SimpleTrigger.RepeatIndefinitely,
                                            TimeSpan.FromHours(24));