# Finding the date of an event based on related events **URL:** \ **Category:** Ruby\ **Created:** [July 18, 2008, 6:28pm UTC](https://www.ruby-forum.com/t/finding-the-date-of-an-event-based-on-related-events/143449 "2008-07-18T18:28:10Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Kaldrenon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/59ef9b/32.png) [@Kaldrenon](https://www.ruby-forum.com/u/Kaldrenon)\ **Post date:** [July 18, 2008, 6:28pm UTC](https://www.ruby-forum.com/t/finding-the-date-of-an-event-based-on-related-events/143449/1 "2008-07-18T18:28:10Z")
Hi all, I’m doing some planning to write a simple utility program for maintaining my schedule. The basic scenario is that, in my job, I have a series of multi-stage procedures to perform, and for each instance of the procedure, the stages need to happen a fixed number of business days apart (i.e, if step one happens on Monday, step two is Friday, but if step one is Tuesday, step two will be the following Monday). As one of the first steps of the program, I’m going to write a script to quickly spit out the calendar dates of all steps given the date of the first and the relative date (in business days) of all the others. My question is, can you help me drum up a ‘smart’ way to take weekends and holidays into account? I know that with Ruby’s Date class you can use the - (minus) operator to subtract x days from the date of an existing event. which is how I can find the exact date once I’ve determined the number of total days it will be before it has been x business days. But the “human” solution to the problem isn’t very efficient - iterating over the days with a counter, checking Date.wday, ignoring days that return 0 and 6, and spitting back the date at which the counter reaches x. I’d like to find a more elegant and computationally efficient solution. If you’ve worked out this problem before, or a better solution seems readily available to you, I’d love input. If my explanation was unclear, I’ll gladly clarify anything. -Andrew Fallows ---
**Author:** ![Kaldrenon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/59ef9b/32.png) [@Kaldrenon](https://www.ruby-forum.com/u/Kaldrenon)\ **Post date:** [July 19, 2008, 12:09am UTC](https://www.ruby-forum.com/t/finding-the-date-of-an-event-based-on-related-events/143449/2 "2008-07-19T00:09:13Z")
Kaldrenon wrote: > Hi all, > > I’m doing some planning to write a simple utility program for > maintaining my schedule. The basic scenario is that, in my job, I have > a series of multi-stage procedures to perform, and for each instance > of the procedure, the stages need to happen a fixed number of business > days apart (i.e, if step one happens on Monday, step two is Friday, > but if step one is Tuesday, step two will be the following Monday). As > one of the first steps of the program, I’m going to write a script to > quickly spit out the calendar dates of all steps given the date of the > first and the relative date (in business days) of all the others. > > My question is, can you help me drum up a ‘smart’ way to take weekends > and holidays into account? > (…) > > -Andrew Fallows To exclude just the weekends you could do class Date def add\_workdays(n) days\_to\_add =((self.cwday+n-1)/5)\*2 +n self + days\_to\_add end end Which returns a new Date and seems to work with negative n’s. (Just wrote this code, don’t know if it’s bullet proof). Holidays are a complication.Ideally the solution would allow for different holidays for different countries. Working hours could be specified, to enable calculating exactly when a 14 hour job starting on friday 24 december 15:15 in the US would finish. Two applications I work with have these features. I’m not aware of a ruby solution/gem. Regards, Siep ---
**Author:** ![Kaldrenon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/59ef9b/32.png) [@Kaldrenon](https://www.ruby-forum.com/u/Kaldrenon)\ **Post date:** [July 19, 2008, 1:03pm UTC](https://www.ruby-forum.com/t/finding-the-date-of-an-event-based-on-related-events/143449/3 "2008-07-19T13:03:57Z")
On Fri, Jul 18, 2008 at 5:04 PM, Siep K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > wrote this code, don’t know if it’s bullet proof). > It isn’t. It won’t work if you start from a weekend day. Use today (Saturday), and do d = Date.today.add\_workdays(5) puts d =\> 2008-07-28 I like the approach, though. Todd ---
**Author:** ![Kaldrenon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/59ef9b/32.png) [@Kaldrenon](https://www.ruby-forum.com/u/Kaldrenon)\ **Post date:** [July 19, 2008, 1:24pm UTC](https://www.ruby-forum.com/t/finding-the-date-of-an-event-based-on-related-events/143449/4 "2008-07-19T13:24:16Z")
-------- Original-Nachricht -------- > Datum: Sat, 19 Jul 2008 01:20:12 +0900 > Von: Kaldrenon [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > An: removed\_email\_address@domain.invalid > Betreff: Finding the date of an event based on related events. > first and the relative date (in business days) of all the others. > days that return 0 and 6, and spitting back the date at which the > counter reaches x. I’d like to find a more elegant and computationally > efficient solution. > > If you’ve worked out this problem before, or a better solution seems > readily available to you, I’d love input. If my explanation was > unclear, I’ll gladly clarify anything. > > -Andrew Fallows Dear Andrew, reading previous responses to your post, I’d like to mention that you can get a list of public holidays from the Wikipedia [List of holidays by country - Wikipedia](http://en.wikipedia.org/wiki/List_of_holidays_by_country), for many countries, the movable holidays are mostly Easter and Pentecost, there is a listing of the Easter dates here (and Pentecost is, I believe, just 7 weeks later): [http://www.assa.org.au/edm.html#List20](http://www.assa.org.au/edm.html#List20) and, secondly, that for the main task you have – scheduling — you could use a “Constraint Programming” framework, such as this: [http://gecoder.rubyforge.org/](http://gecoder.rubyforge.org/) where you input all the conditions you have and get back a solution… Best regards, Axel ---
**Author:** ![Kaldrenon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/59ef9b/32.png) [@Kaldrenon](https://www.ruby-forum.com/u/Kaldrenon)\ **Post date:** [July 19, 2008, 8:52pm UTC](https://www.ruby-forum.com/t/finding-the-date-of-an-event-based-on-related-events/143449/5 "2008-07-19T20:52:17Z")
On Sat, Jul 19, 2008 at 1:13 PM, Todd B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > w\_days = [nil] + (Date.today…Date.today + > some\_number\_of\_days).map.select {|day| (day.cwday / 5).zero?} That should be a 6 not a 5. Todd ---
**Author:** ![Kaldrenon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/59ef9b/32.png) [@Kaldrenon](https://www.ruby-forum.com/u/Kaldrenon)\ **Post date:** [July 19, 2008, 8:15pm UTC](https://www.ruby-forum.com/t/finding-the-date-of-an-event-based-on-related-events/143449/6 "2008-07-19T20:15:23Z")
On Fri, Jul 18, 2008 at 11:20 AM, Kaldrenon [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > first and the relative date (in business days) of all the others. > days that return 0 and 6, and spitting back the date at which the > counter reaches x. I’d like to find a more elegant and computationally > efficient solution. > > If you’ve worked out this problem before, or a better solution seems > readily available to you, I’d love input. If my explanation was > unclear, I’ll gladly clarify anything. > > -Andrew Fallows Maybe build a calendar beforehand that only includes work days… w\_days = [nil] + (Date.today…Date.today + some\_number\_of\_days).map.select {|day| (day.cwday / 5).zero?} …and then later… w\_days -= holiday\_dates #which is an array of holiday Date objects chosen by you …which afterwards you could walk through 6 at a time. That, to me is somewhat elegant and robust, but Siep’s idea will work if the script/program will always run from a weekday. You will notice the peculiarity that Saturday acts like Monday and Sunday acts like Tuesday with Siep’s example. I’d probably create a WorkCalendar class, though. Todd ---
**Author:** ![Kaldrenon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/59ef9b/32.png) [@Kaldrenon](https://www.ruby-forum.com/u/Kaldrenon)\ **Post date:** [July 21, 2008, 12:14pm UTC](https://www.ruby-forum.com/t/finding-the-date-of-an-event-based-on-related-events/143449/7 "2008-07-21T12:14:47Z")
Following error message: ===\> Patching for ruby18-gems-1.2.0 ===\> ruby18-gems-1.2.0 depends on file: /usr/local/bin/ruby18 - found ===\> Applying FreeBSD patches for ruby18-gems-1.2.0 =\> Patch patch-lib-rubygems-source\_info\_cache.rb failed to apply cleanly. \*\*\* Error code 1 Stop in /usr/ports/devel/ruby-gems FreeBSD \*\*\*.vizion2000.net 7.0-STABLE FreeBSD 7.0-STABLE #0: Wed Jul 16 09:27:38 PDT 2008 @\*\*\*.vizion2000.net:/usr/obj/usr/src/sys/GENERIC amd64 This system has just been upgraded from 6.3 to 7.0-Stable. Is there a possible connection here? After getting this error I checked to make sure the port tree was uptofate and tried again with the same result. I am currently recompiling ruby\* ports on the system after a portsclean with: portupgrade -fr ruby\* Has anyone else experienced a similar problem? I will report result of recompile when it finishes. David ---
**Author:** ![Kaldrenon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/59ef9b/32.png) [@Kaldrenon](https://www.ruby-forum.com/u/Kaldrenon)\ **Post date:** [July 21, 2008, 12:20pm UTC](https://www.ruby-forum.com/t/finding-the-date-of-an-event-based-on-related-events/143449/8 "2008-07-21T12:20:03Z")
> ===\> Patching for ruby18-gems-1.2.0 > 09:27:38 PDT 2008 > portupgrade -fr ruby\* > Has anyone else experienced a similar problem? > I will report result of recompile when it finishes. > > David The recompile produced the same result for ruby-gems. Is a pr needed here or is someone on to it already? David ---
**Author:** ![Kaldrenon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/59ef9b/32.png) [@Kaldrenon](https://www.ruby-forum.com/u/Kaldrenon)\ **Post date:** [July 21, 2008, 4:10pm UTC](https://www.ruby-forum.com/t/finding-the-date-of-an-event-based-on-related-events/143449/9 "2008-07-21T16:10:54Z")
On Jul 19, 2:08 pm, Todd B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > That, to me is somewhat elegant and robust, but Siep’s idea will work > if the script/program will always run from a weekday. The general idea is that it will, given that the input will always be an event that the user is scheduling, and the context is scheduling for a M-F 5-day workweek setting. However, in the interest of versatility, I like to avoid coding in a “assuming the user knows what format to input” setup. Thanks to all for the replies and advice! This is kind of a side project for me at the moment, so I haven’t yet gotten a chance to implement any of these things or test them, but I will be sure to get back to the group with my results when I do. As for my holiday list, I think the simplest initial concept, for testing the basic functionality, is a Hash of Date objects based on my employer’s list of holidays for which employees get time off, as opposed to a list of all US holidays, but I’ll look into a flexible way to plug in a holiday list at a later point. Thanks again, Andrew