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I have this cron expression "0 0 L-3 * *".
It worked fine until after that point in time, then is crashed with the exception below.

System.ArgumentException: Invalid value '2375713936.2261' for parameter 'interval'.
at System.Timers.Timer..ctor(Double interval)
at Domain.Services.CronJobService.ScheduleJob(CancellationToken cancellationToken) in E:\SourceCode\LDS\src\Domain\Domain.Services\CronJobService.cs:line 37
at Domain.Services.CronJobService.StartAsync(CancellationToken cancellationToken) in E:\SourceCode\LDS\src\Domain\Domain.Services\CronJobService.cs:line 24
at LDS.ReportService.CassetteRefilList.StartAsync(CancellationToken cancellationToken) in E:\SourceCode\LDS\src\LDS\LDS.ReportService\Reports\CassetteRefilList.cs:line 46
at Microsoft.Extensions.Hosting.Internal.Host.StartAsync(CancellationToken cancellationToken)
at Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.RunAsync(IHost host, CancellationToken token)
at Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.RunAsync(IHost host, CancellationToken token)
at Microsoft.Extensions.Hosting.HostingAbstractionsHostExtensions.Run(IHost host)

If I change the expression to "0 0 L * *" there is no issue.

I tried changing the expression
"0 0 24 * *" - Works
"0 0 25 * *" - Exception all expressions with the date above 24 give the exception.

any ideas?

This dll is really giving correct result. Just curious to know if there is any version available who can handle year as well. Currently, 6 octet cron expression is allowed.

I have a job running on the last thursday of every month, "0 0 8 * * THUL". (which will occur in either the 3rd or 4th week of the month)

Is it possible to create an expression that provides the occurences 3 days before the occurences returned from the above expression? ("every monday of the week of the last thursday in month").

I need the GetOccurrences method to calculate the next occurrences based on the from date,

Eg: My cron expression is ' Occurs on day 1 of every 3 months' and from date is 'Feb 20 2018' , then the occurences should be

• 01-May-2018
• 01-Aug-2018
• 01-Nov 2018 etc

But the current behaviour is always taking the default date as

• 01-April-2018
• 01-Jul-2018
• 01-Oct-2018

Need help to figure out the issue

It seems Cronos only supports Gregorian calendar, Do you have any workaround to use different calendars with Cronos?

Is supporting for other calendars in you future plans?

Hi! I am trying to familiarize myself with the scenarios in which the GetNextOccurrence can return a DateTime? with null value, and I have a hard time understanding the logic behind the behavior. It seems that calculating the next occurrence for dates after the year 2100 is unsuccessful about half of the time. Here is a minimal example:

string expression = "0 0 15 6 *"; // June, 15
var cronExpression = CronExpression.Parse(expression);
Console.WriteLine($"Expression: {cronExpression}");
for (int i = 1; i <= 24; i++)
{
    var fromUtc = new DateTime(2150, 1, 1, 0, 0, 0, DateTimeKind.Utc).AddMonths(i);
    var nextUtc = cronExpression.GetNextOccurrence(fromUtc);
    Console.WriteLine($"Date: {fromUtc}, NextOccurrence: {(nextUtc.HasValue ? nextUtc.Value.ToString() : "-")}");
}

Output:

Expression: 0 0 0 15 6 *
Date: 02/01/2150 00:00:00, NextOccurrence: 06/15/2150 00:00:00
Date: 03/01/2150 00:00:00, NextOccurrence: 06/15/2150 00:00:00
Date: 04/01/2150 00:00:00, NextOccurrence: 06/15/2150 00:00:00
Date: 05/01/2150 00:00:00, NextOccurrence: 06/15/2150 00:00:00
Date: 06/01/2150 00:00:00, NextOccurrence: 06/15/2150 00:00:00
Date: 07/01/2150 00:00:00, NextOccurrence: -
Date: 08/01/2150 00:00:00, NextOccurrence: -
Date: 09/01/2150 00:00:00, NextOccurrence: -
Date: 10/01/2150 00:00:00, NextOccurrence: -
Date: 11/01/2150 00:00:00, NextOccurrence: -
Date: 12/01/2150 00:00:00, NextOccurrence: -
Date: 01/01/2151 00:00:00, NextOccurrence: 06/15/2151 00:00:00
Date: 02/01/2151 00:00:00, NextOccurrence: 06/15/2151 00:00:00
Date: 03/01/2151 00:00:00, NextOccurrence: 06/15/2151 00:00:00
Date: 04/01/2151 00:00:00, NextOccurrence: 06/15/2151 00:00:00
Date: 05/01/2151 00:00:00, NextOccurrence: 06/15/2151 00:00:00
Date: 06/01/2151 00:00:00, NextOccurrence: 06/15/2151 00:00:00
Date: 07/01/2151 00:00:00, NextOccurrence: -
Date: 08/01/2151 00:00:00, NextOccurrence: -
Date: 09/01/2151 00:00:00, NextOccurrence: -
Date: 10/01/2151 00:00:00, NextOccurrence: -
Date: 11/01/2151 00:00:00, NextOccurrence: -
Date: 12/01/2151 00:00:00, NextOccurrence: -
Date: 01/01/2152 00:00:00, NextOccurrence: 06/15/2152 00:00:00

Live demo.

Could you explain why the calculation fails when the month+day of the starting date is
larger than the month+day in the Cron expression?

Thanks!

Hi,

I'm having an issues with Cronos v0.6.2 when trying to generates a list of occurrences across last daylight saving change.

Here is a simple code to reproduce. It try to generate each 1/4h from 00:00 utc to 03:00 utc the night of dst for the Western Europe timezone.

        var tzi = TimeZoneInfo.FindSystemTimeZoneById("W. Europe Standard Time");
        var begin = new DateTime(2017, 10, 29, 00, 00, 00, DateTimeKind.Utc);
        var end = new DateTime(2017, 10, 29, 03, 00, 00, DateTimeKind.Utc);
        var expr = CronExpression.Parse("0/15 * * * *");

        var dates = expr.GetOccurrences(begin, end, tzi);

        foreach (var d in dates)
        {
            Console.WriteLine(d);
        }

        Console.ReadKey();

Result is :

29-10-17 01:00:00
29-10-17 01:15:00
29-10-17 01:30:00
29-10-17 01:45:00
29-10-17 02:15:00
29-10-17 02:30:00
29-10-17 02:45:00

Unless I missed something, expected result would be :

29-10-17 01:00:00
29-10-17 01:15:00
29-10-17 01:30:00
29-10-17 01:45:00
29-10-17 02:00:00
29-10-17 02:15:00
29-10-17 02:30:00
29-10-17 02:45:00

I'm currently evaluating hangfire and need to be able to support a date range when the job should run. I saw in commit 8dc1b11 that year support was removed since it caused ambiguity with the seconds field so it seems like I would have to place those date checks in the job itself which I'd rather not do. Would it be possible to add year support only if there are 7 fields specified in the cron expression meaning if you want to specify a year, you also have to specify seconds?

Hi there,

I wanted to know whether there was the possibility of having a signed version of the assembly distributed to NuGet? I was thinking of using this framework as a dependency of one of my own (WIP) frameworks, but unfortunately mine is signed and won't build as this package doesn't have a strong name.

Thanks

hi,
I am getting error when I am setting CronExpression for month.

Error Message: Invalid value '2376995117.7807' for parameter 'interval'.'

// Cron setting
services.AddCronJob(c =>
{
c.TimeZoneInfo = TimeZoneInfo.Local;
c.CronExpression = @"0 0 1 * *";
});

when google for this issue I found that System.Timers.Timer only store maximum 25 day time value

            var cronExp = CronExpression.Parse("0 0 * * * ?", CronFormat.IncludeSeconds);
            var nrt = cronExp.GetNextOccurrence(DateTime.UtcNow, false);
            Console.WriteLine($"{nrt} - {nrt?.Kind}");
            var nrt2 = cronExp.GetNextOccurrence(DateTime.UtcNow, true);
            Console.WriteLine($"{nrt2} - {nrt2?.Kind}");

            Console.WriteLine();

            DateTimeOffset? nrt3 = cronExp.GetNextOccurrence(DateTimeOffset.UtcNow, TimeZoneInfo.Local, false);
            Console.WriteLine($"{nrt3} - {nrt3?.DateTime.Kind}");
            DateTimeOffset? nrt4 = cronExp.GetNextOccurrence(DateTimeOffset.UtcNow, TimeZoneInfo.Local, true);
            Console.WriteLine($"{nrt4} - {nrt4?.DateTime.Kind}");

return are same.

2019-03-21 6:00:00 AM - Utc
2019-03-21 6:00:00 AM - Utc

2019-03-21 2:00:00 PM +08:00 - Unspecified
2019-03-21 2:00:00 PM +08:00 - Unspecified

Hi everyone,

could be possible to have one of these two methods to avoid everytime to catch the CronFormatException?
If you allow users to contribute on the project, I'll be enthusiast to create a PR on that.

Thanks for attention.

If you look at the configuration Ii have below using this library, I selected the following:
"First Monday of each Month" (starting in April)

However the first occurence returns back the current month which is March. the same issue happens for each month of the year selected where I am expecting it to return next month, not the current month. This seems to be happening somehwere within the libray when using the get next occurence method.

I'm using library ver 0.71

Could you add .Net Standard 2 support to the NuGet package so we don't have an explicit dependency on NetStandard.Library, please?

I want to run a job every three or five (or n) days from now, and I wrote the expression '0 8 */5 * *'.

If now is '2018/05/17',

and I get the occurrences:

0 8 */5 * *
2018/5/21 8:00:00
2018/5/26 8:00:00
2018/5/31 8:00:00
2018/6/1 8:00:00
2018/6/6 8:00:00
2018/6/11 8:00:00
2018/6/16 8:00:00
2018/6/21 8:00:00
2018/6/26 8:00:00
2018/7/1 8:00:00
2018/7/6 8:00:00
2018/7/11 8:00:00
2018/7/16 8:00:00
2018/7/21 8:00:00
2018/7/26 8:00:00
2018/7/31 8:00:00
2018/8/1 8:00:00
2018/8/6 8:00:00

but, which I expected are:

0 8 */5 * *
2018/5/22 8:00:00     -- wrong
2018/5/27 8:00:00     -- wrong
2018/6/1 8:00:00
2018/6/6 8:00:00
2018/6/11 8:00:00
2018/6/16 8:00:00
2018/6/21 8:00:00
2018/6/26 8:00:00
2018/7/1 8:00:00
2018/7/6 8:00:00
2018/7/11 8:00:00
2018/7/16 8:00:00
2018/7/21 8:00:00
2018/7/26 8:00:00
2018/7/31 8:00:00
2018/8/5 8:00:00      -- wrong
2018/8/10 8:00:00     -- wrong

Do the cron expression that I wrote is wrong? Or the Cronos don't support this situation?

Any one help me?

Thanks,
Leaf

Hello.

Find the case CronExpression.Parse("* * * * */2,3") that fails with exception:

Minutes: Unexpected character ','.

And it not work at any position (minute, hour, etc.). Is it a bug? Or it's partial support for not standard special character / ?

Further to #36 (comment), is there any plan to support NodaTime fully, either via an additional shim package or just by including NodaTime in the core functionality?

For example, there's no easy way to fully implement

ZonedDateTime? GetNextOccurence(ZonedDateTime fromZoned, bool inclusive)

externally as you can't guarantee there's an equivalent System.TimeZoneInfo for any given NodaTime.DateTimeZone which is more feature rich. Whereas you can largely guarantee the opposite is true.

0 0 15,L * ? should produce the 15th of the month or the Last day of the month. Instead it complains about the L not being a number.

Am I missing something or should this be supported?

Thanks
Jim

Hi. I have a problem getting next occurrence time or i just miss something in Cronos documentation.

Problem:
User can set scheduler, which is done with the cron expression. User can set date and time and interval. For example 1.2.2012 15:00:00 every two days. But the date doesn't change often, only when user set new time or interval, what means if today is 20.2.2012 12:00:00, then GetNextOccurrence() get the 3.2.2012 15:00:00 as result, but i want to get 21.2.2012, which is the next relevant run time.
Workaround:

var occs = expression.GetOccurrences(schedule.Time, DateTime.UtcNow, TimeZoneInfo.Local).ToList();
job.NextRunTime = expression.GetNextOccurrence(occs.Last(), TimeZoneInfo.Local);

I just get all occurrences till today and then i use last one to get the ACTUAL next one.

Does it make sense to have a function like: GetNextOccurrenceBasedOnDateTimeNow(...)?

Thank You

A Step is working with every date part place holder. But the Day of the week place holder not considering */5 (with n number of Steps ahead when an weekly interval is given)

Parsing of "* * * * * " (six stars here, markdown hides a star) throws an exception
CronExpression.Parse(" * * * * * *")

Cronos.CronFormatException: Unexpected character '*'.
at Cronos.CronExpression.ThrowFormatException(String format, Object[] args) in C:\projects\cronos\src\Cronos\CronExpression.cs:line 1014
at Cronos.CronExpression.Parse(String expression) in C:\projects\cronos\src\Cronos\CronExpression.cs:line 91

In the README, at this paragraph:
https://github.com/HangfireIO/Cronos/blob/master/README.md#getting-occurrences-within-a-range.

The return type should be IEnumerable<DateTime> instead of DateTime?.
IEnumerable<DateTime> occurrences = expression.GetOccurrences( DateTime.UtcNow, DateTime.UtcNow.AddYears(1), fromInclusive: true, toInclusive: false);

Wrong value reported for next occurrence, ignores remaining time for this current date.

Consider the following:

    var strExpression = "25 23 */3 * *";
    var cronExpression = Cronos.CronExpression.Parse(strExpression, Cronos.CronFormat.Standard);
    var nextOccurrence = cronExpression.GetNextOccurrence(DateTime.UtcNow);

    var now = DateTime.UtcNow; // 2020-09-30 16:32:00
    var nextFireShouldBe = new DateTime(now.Year, now.Month, now.Day, 23, 25, 0);

    //nextOccurrence    => 2020-10-01 23:25:00
    //nextFireShouldBe  => 2020-09-30 23:25:00

Next occurrence should be on same date, but is pushed for tomorrow instead

Hi,

First of all, your library is awesome! I do however have issues with multiple days of week in the MontlyDoW schedule.
34 15 * 1,12 2#1,2#L is the cron string I'm using. Parsing fails with:
Days of week: Unexpected character ','.
Now if I leave a single value for days of week such as 34 15 * 1,12 2#1 it works as expected. Is there any way to make it work with multiple values?

Thanks.
Bogdan

RecurringJob.AddOrUpdate( () => Console.WriteLine("Recurring!"), "* * * * * *", queue: "test");

but in HangfireIO/Cronos's README.md

                                   Allowed values    Allowed special characters   Comment

┌───────────── second (optional) 0-59 * , - /
│ ┌───────────── minute 0-59 * , - /
│ │ ┌───────────── hour 0-23 * , - /
│ │ │ ┌───────────── day of month 1-31 * , - / L W ?
│ │ │ │ ┌───────────── month 1-12 or JAN-DEC * , - /
│ │ │ │ │ ┌───────────── day of week 0-6 or SUN-SAT * , - / # L ? Both 0 and 7 means SUN
│ │ │ │ │ │

Hi,
I'm using Cronos inside application which read user configurations which could have standard minutes form or extended with seconds. Problem is, i do not know if user enter one or another and Parse() method without second parameter throws Cronos.CronFormatException: Unexpected character '*'..
How should i detect if it is standard form or extended when Cronos can't detect it by itself?

When cron expression is set to run job at every 30+ mints, for example "*/40 * * * *", it shows next occurrences as

8/6/2021 3:40:00 AM
8/6/2021 4:00:00 AM
8/6/2021 4:40:00 AM
8/6/2021 5:00:00 AM
8/6/2021 5:40:00 AM
8/6/2021 6:00:00 AM
8/6/2021 6:40:00 AM
8/6/2021 7:00:00 AM
8/6/2021 7:40:00 AM
8/6/2021 8:00:00 AM

It's not continuing the 40 mints gap between the executions.

Would you please consider returning the return the DateTime when a task would have been due going back in time.

I am currently using the real hack

_expression.GetOccurrences(scheduled.AddDays(-60), scheduled, _timeZoneInfo, false, false).Last();

Frankly, the "0 0 1 8 0" was a well-formed value, It indicates "At 00:00 on day-of-month 1 and on Sunday in August".
but it can not be parsed on version 0.7.0
Any latest implementation of this project?

deleted, see other post.

I see csproj has version 1.0, but published Cronos nuget has version 0.7 and there is also Longbow.Cronos nuget with version 1.0.

What nuget should be used - is current?

Marek

Is this not a valid cron expression?

0 0 11 * 7 SAT

Cronos fails with : 'Unexpected character 'S'.'

Hi
first of all I want to thank you for the great library.
One thing doesn't seem to be working correctly. I am in Europe and DST was applied on 28/3/21 from 2 to 3 am CET which is one hour ahead of UTC. When I ask for the next occurrence 1 minute before DST it returns the right UTC timestamp. Doing the same at DST change it returns the next occurrence 1 week later.
Dim expression As Cronos.CronExpression = Cronos.CronExpression.Parse("0 2 * * 0")
Dim nextOccurrence As DateTimeOffset = expression.GetNextOccurrence(start, timeZone, True)
Return nextOccurrence.DateTime

log time - GetNextOccurrence - start
2021-03-28 01:59:01,812 - 2021-03-28T01:00:00.0000000 - 2021-03-28T00:59:00.0000000Z
2021-03-28 03:00:01,163 - 2021-04-04T00:00:00.0000000 - 2021-03-28T01:00:00.0000000Z

Am I doing something wrong here?
Thanks.
Martin

This is a feature request for a new method on CronExpression that provides a human-readable description of the cron expression.

For example 30 12 LW * * would show 12:30 on the last weekday of the month

Hi,

The documentation lists support for non-standard characters like L, W, # and their combinations.

Could F (First) be added?

Thanks

I could very well be wrong about this. That happens a lot, but given the following setup, I'd expect all four tests to pass here.

private readonly TimeZoneInfo EST = TimeZoneInfo.FindSystemTimeZoneById("America/New_York");
private readonly DateTimeOffset Jan1st2000 = new DateTimeOffset(2000, 01, 01, 00, 00, 00, new TimeSpan(-4, 0, 0));

// Asking just BEFORE midnight should yield the 1st (Works)
CronExpression.Parse("0 0 * * 6").GetNextOccurrence(Jan1st2000.AddMilliseconds(-1), EST).ShouldBe(new DateTime(2000, 01, 01));

// Asking exactly AT midnight should also yield the 1st (Works)
CronExpression.Parse("0 0 * * 6").GetNextOccurrence(Jan1st2000, EST).ShouldBe(new DateTime(2000, 01, 01));

// Asking just AFTER midnight should yield the 8th (Only the first one works)
CronExpression.Parse("0 0 * * 6").GetNextOccurrence(Jan1st2000.AddHours(1), EST).ShouldBe(new DateTime(2000, 01, 08));
CronExpression.Parse("0 0 * * 6").GetNextOccurrence(Jan1st2000.AddSeconds(61), EST).ShouldBe(new DateTime(2000, 01, 08));

Once I'm outside the first hour, it correctly jumps to the next Saturday, but shouldn't moving outside the first minute also yield the next Saturday? The individual fields are supposed to be AND-ed together, right? If I've moved my "now" outside the first minute of the first hour, then it shouldn't count again until the next Saturday midnight... right?

Apologies if I'm overlooking the obvious here. I've been staring at this too long.

Hi guys, I'm using NCronTab right now because it has a GetNextOccurence*s* method that returns an IEnumerable<T> of DateTime's when you give it a date range. Is there a good way to get the same result from your library? Thanks!

Hi, I am wondering if there are plans to support the latest LTS versions of .Net. I know some projects wish to stick to netstandard for compatibility purposes, but it seems worth asking about at least. I can make an attempt at a PR with this update as well, just let me know if you have any recommended steps to test/verify before I begin.

Hi, I am working on a small project for scheduling custom scripts from db. I was trying to check if DateTime.UtcNow is a valid occurance, but I came across the lack of such an option. I think it could be a good feature.

My users have just asked if they can change the current schedule of every 30 mins between 10am and 5pm to also include 5pm.

I can't see a way of doing this without also including 5:30pm therefore i would like to have an array of two expressions built into one so that GetNextOccurrence will get the next one from either expression.

            var expressions = new string[]
            {
                "0,30 10-16 * * 1-5", 
                "0 17 * * 1-5"
            };
            var cronosExpression = CronExpression.Parse(expressions);

I've reworked my app to handle this in my IHostedService manually but there might be others who will need something like this in the future too, it's easy enough to do in a Linux crontab because you just run the same script twice.

0,30 10-16 * * 1-5  /opt/example.sh
0 17 * * 1-5        /opt/example.sh

Hi!

Could be me misunderstanding something, but im getting different results with the following call:

DateTime startTime = {'5/20/2022 12:00:00 AM' }; //obv as a DateTime object
DateTime endTime= {'5/31/2022 12:00:00 AM' }; // obv as a DateTime object
string expression = '0 0 9 * * 1,2,3,4,5';
var cron = cronExpression.Parse(expression , CronFormat.IncludeSeconds);
cronExpression.GetOccurances(startTime, endTime, true, true).
this returns, as expected the following:
5/20/2022 9:00
5/23/2022 9:00
5/24/2022 9:00
5/25/2022 9:00
5/26/2022 9:00
5/27/2022 9:00
5/30/2022 9:00

however, changing the expression to the following
string expression = '0 0 0 * * 1,2,3,4,5';

removes 5/20 from the list, despite it being the exact same call?

I could theoretically move the input times back by a second, but that's a hacky fix id rather not do.

Again, not sure if this is expected behavior, or if I'm just being dumb. Let me know if you can help. Thanks!

expression "0 0 4 ? * * *" generated on site

CronExpression.Parse("0 0 4 ? * * *", CronFormat.Standard) \\ Cronos.CronFormatException: "Unexpected character '*'."

CronExpression.Parse("0 0 4 ? * * *", CronFormat.IncludeSeconds) \\ Cronos.CronFormatException: "Unexpected character '*'."

why can't it be parsed?

Cronos 0.7.1

Hello!

Today I found some error when try to parse 0 0 15,28 * * (in 15 and 28 day of each month at midnight) expression. In this case I used format without seconds, just five positions. But when I used CronExpression.Parse method, then I saw get exception with message Cronos.CronFormatException: Hours: Value must be a number between 0 and 23 (all inclusive).. I checked tests with commas and don't found this.

It is problem with autodetect format or not?

P.S. I fixed this problem when used format with seconds, just adding zero in seconds position 0 0 0 15,28 * *.

We use hangfire pro and i'd like to have jobs run on the last sunday for first sunday of every month. Is that possible?

I tried using the 0 0/3 * 1/1 * ? Cron expression but it tells me the ? character is unexpected.

I don't understand why it has issues parsing this since I've been using it with Quartz.Net and it works fine.

What is the problem?

Thanks

It looks like a ToString method is not symetric - what I mean by that is that one would expect from CronExpression to pass through Parse→ToString→Parse cycle to produce an equivalent expression as in the first parse.

The motivation for that is that stringified cron expression may be i.e. serialized and restored later.

Simple example to reproduce an issue:

var expr = CronExpression.Parse("*/5 * * * *");
var serialized = expr.ToString(); // 0 0,5,10,15,20,25,30,35,40,45,50,55 * * * *
var expr2 = CronExpression.Parse(serialized);
/*
Cronos.CronFormatException
Days of month: Value must be a number between 1 and 31 (all inclusive).
   at Cronos.CronExpression.ThrowFormatException(CronField field, String format, Object[] args)
   at Cronos.CronExpression.ParseDayOfMonth(Char*& pointer, CronExpressionFlag& flags, Byte& lastDayOffset)
   at Cronos.CronExpression.Parse(String expression, CronFormat format)
*/

I think, the easiest way to solve this, would be to attach original cron expression string as an extra field of the CronExpression class:

• Expression strings are small and usually written by humans, so keeping them arround won't occupy much memory.
• This would make ToString method much faster (useful i.e. for logging).
• The whole class would still be under 64 bytes, therefore fit into CPU cache line.

Hello everyone,

I am trying to run a script on both the first and second weekday of the month. While the first weekday is fine ( [0 0 1W * *] as in nearest weekday to 1st of month), I can't find a solution for the second weekday. 2W only works if the 1st falls within the Mon-Thu range. Otherwise 1W and 2W will be mapped to the same day. Does somebody have a solution for that? This would be an awesome feature to have.

Thanks and best regards

such like:
0 15 10 ? * * 2019-2019

Hi,
I would like to ask if there is a plan to support multple day of week specifiers.
For example this cron expression is currenlty not supported:
0 0 11 ? 8/2 SAT,SUN#3
It means: "At 11:00 AM, on the third Saturday and Sunday of the month, every 2 months, August through December" and allow to apply the "#" specifier to two days of week Saturday and Sunday.
Thanks, regards,
D