[Remind-Fans] Event on last Friday in month and on the consecutive day

[Max]

Hi,

Two local events, one taking place on the last Saturday in April and
the day before (Friday) and the other one one the last Friday in
August and the day after (Saturday). Consequently, for the first
event, Friday and Saturday always fall into the same month and my
current remind rule is as follows:

   REM Sat 1 May --7 SATISFY 1
   REM [trigger(trigdate() - 0 )] MSG Event 1%
   REM [trigger(trigdate() - 1 )] MSG Event 1%

However, Friday and Saturday of the second event could fall into
consecutive months. I tried the following rule but it fails to trigger
on Saturday, even if it falls within the same month:

   REM Fri 1 Sep --7 SATISFY 1
   REM [trigger(trigdate() - 0 )] MSG Event 2%
   REM [trigger(trigdate() + 1 )] MSG Event 2%

How could a rule for the second event look like? Does anyone have a
more generic or more elegant solution to the problem "trigdate +/- n
days before/after"?

Any clues?

Thanks.