What version of the SDK are you using? You can check with q2 inspect.

FIXED (Somewhat)

The error I kept getting wasn’t just the whole date invalid what-have-you; there was ANOTHER line:

_q2:24: bad math expression: operand expected at end of string

Given that I didn’t enter any kind of math expression, I went looking at antilles_completion.zsh

The error:
This block of code:

if [ $(uname -s) = 'Darwin' ]; then
    date -v -5M '+%s' > $LASTRUN_PATH
else
    date --date='5 minutes ago' '+%s' > $LASTRUN_PATH
fi

Continued from above:

I replaced that block with:

if command -v gdate &> /dev/null; then
    gdate -d '-5 minutes' '+%s' > $LASTRUN_PATH
elif command -v date &> /dev/null; then
    date -d '-5 minutes' '+%s' > $LASTRUN_PATH
else
    echo "Error: Unable to find a suitable 'date' command."
    exit 1
fi

And now completion is working as expected. Hopefully this is helpful to other folks, and if anyone has additional insight, I'm all ears.