writing-weekday-matches-datelisted

# A weekday next to a date is checked against the calendar If a text says "Monday, September 21", a calendar confirms September 21 is a Monday before it goes out. Never write the weekday and date together from memory. ## Why The cost is asymmetric. For us a wrong weekday is one correction. For the person on the other side it is a lost slot, and they will not notice the mismatch: they write down one of the two and trust it. It happened to us. A client was told twice, in writing, that a prospect call was on "Monday the 25th". The 25th was a Tuesday. We corrected it with the prospect, but the client had already put the wrong day in their calendar, and the fix needed a separate message and an apology. The first version of our check also failed, in an instructive way. It accepted a match in any of three nearby years. The 25th of that month had been a Monday the year before, so the check stayed silent on exactly the mistake it was written for. A date without a year means the nearest such date, and only that one. ## How to apply 1. Take the weekday from a calendar, not from your head. When you write a date, compute the weekday. 2. Before sending, run the check on the final text: `python3 scripts/weekday_check.py message.txt` or pipe it: `echo "$TEXT" | python3 scripts/weekday_check.py -` 3. Year: if the date has a year, use it. If not, use the date nearest to today. 4. The check is permissive on purpose. It fails only when the weekday sits right next to the date (a spac