This may have already been reported, but I'll do it anyway

DF 20.0.7 DAW SQL Driver MS SQL Express

Code:
Move (dtNow - dtCalibrated) to tsDiff
dTNow is today & dtCalibrated is "blank" - since the DB is old DateTime, it's actually 1753-01-01.

The subtraction gives an error:

TimeSpan contains an invalid value
Error: 4524

I worked around it by setting dtCalibrated to a week ago if blank since I'm checking if there's a >24 hour diff but shouldn't it be able to handle a "blank" date?

Love the "new" DateAddDay, etc. capability, BTW.