[Remind-Fans] Thanksgiving in the U.S.

[Dianne Skoll]

On Wed, 17 Nov 2021 10:15:15 -0500
"Paul M. Foster via Remind-fans" <remind-fans at lists.skoll.ca> wrote:

> There's a rather complicated formula for deriving the U.S.
> Thanksgiving holiday in the Remind wiki. The holiday is on the 4th
> Thursday in November every year. From my read of the remind
> algorithm, it seems as though this would be more simply expressed as:
> "REM Thu Nov 22 MSG Thanksgiving Day". November 22 is the earliest
> day on which this event can occur. Am I missing something?

You are correct... but so is the Wiki. :)

If all you want is a reminder of Thanksgiving Day, then yes:

   REM Thu Nov 22 MSG Thanksgiving Day

is fine.  However, if you want Thanksgiving Day marked as an OMITted
holiday, then the code on the Wiki is better.  The remind manual
page has a section about OMITting movable holidays in the section
DETAILS ABOUT TRIGGER COMPUTATION.

Specifically, this:

  The  main  use of SCANFROM is in situations where you want to calculate
  the positions of floating holidays.  Consider the  Labour  Day  example
  shown  much  earlier.  Labour Day is the first Monday in September.  It
  can move over a range of 7 days.  Consider the following sequence:

       REM Mon 1 Sept SCANFROM [today()-7] SATISFY 1
       OMIT [trigdate()]

       REM Mon AFTER MSG Hello

  The SCANFROM clause makes sure that Remind begins scanning from 7  days
  before  the current date.  This ensures that Labour Day for the current
  year will continue to be triggered until 7 days after it has  occurred.
  This allows you to safely use the AFTER keyword as shown.

Regards,

Dianne.