I'm aware of the "D" date issue in 2021 but any other issues? We are working on updating from 2018 and notice this: In a vanilla query (MySql): 2018 - UPDATED_DT 2024-02-23 091952.0 << note the trailing 0 2021 - UPDATED_DT 2024-02-23 091952

What datatype is the column?

'datetime' and the .0 is not present in the db

I've run into that with integer values that were being treated as double or float, but don't think I've seen in w dates.

Looks like we are using zeroDateTimeBehavior=convertToNull in our connection string to fix an issue that cropped up in 2018 with using 0000-00-00 000000 as a date.

That's a valid date format with milliseconds -- so it's going to depend on how it's formatted. How exactly are you printing those datetime values in your CFML?

This is just what is returned in the query ...

we are just building a json string

Unfortunately, there are no standards for date/time values in JSON 😞

Make sure to also check the serializeJSON(), that has changed as well.