if (a-certain-day-of-week, then "yes", otherwise "no")

How would I go about this?

Column A contains consecutive DATES in the format JJJ J MMM AA ( in Language French (Canada) )

in Column B , I want to make appear, for each Row, the text “yes” if the “JJJ” part of the DATE is a-certain-day-of-week, for example “mer.”, otherwise the text “no” if the DATE in Column A at that same Row is any of the 6 other days of the week.


For mer.:



as usual with dates: Do you have real calc dates (which are integers) or do you have text?

  • In case you have real calc dates then just use: =IF(WEEKDAY(A1;2)=3;"yes";"no") (assuming your date is in A1)
  • In case you have textual dates (and you don’t want to convert to real calc dates) use: =IF(LEFT(A1;3)="mer";"yes";"no")

To see what you have:

  • Set View -> Value Highlighting
  • If the “dates” turn to blue color → you have real calc dates
  • If the “dates” turn to black color → you have textual dates (which are not suitable for calculations)

See also:

[1] - LibreOffice Help - WEEKDAY

[2] - How to convert number text to numeric data

Hope that helps.