How to include dates into my mail merge or why are dates incorrectly formatted?
Excel processes dates in a numeric format, so if you try adding a date field the mail merge will include a numeric value instead of the date you expected.
In order to correctly add a date, simply create a new column (e.g. "DateString") and add the following formula (referencing your date column, in this example A2):
Note the exact formula depends on your Excel language settings, see here for details on how to exactly use the function: https://support.microsoft.com/en-us/office/text-function-20d5ac4d-7b94-49fd-bb38-93d29371225c
This way a new column is created with the date stored as a text and you can configure the way it is displayed automatically (e.g. 14/02/2019 or 2019-02-14 or 14th Feb).