SQL Server’s ISDATE() function checks whether or not an expression is a valid date. However, you may be aware that this function doesn’t work on datetime2 values. On datetime2 values it returns 0, which means it’s not a valid date, even when the value is a valid date.

This is obviously not ideal, because the datetime2 type is a valid date type. Microsoft even recommends that we use datetime2 instead of datetime for our dates, as it aligns with the SQL Standard and it provides more fractional seconds precision.

Anyway, below are three options we can use to check whether a datetime2 value is a valid date.

If you’re getting an error that reads Argument data type datetime2 is invalid for argument 1 of isdate function, it’s because you’re passing a datetime2 value to the ISDATE() function, but this function doesn’t work with datetime2 values.

To fix this issue, either pass a valid date type or use the work around below to provide similar functionality that works with datetime2 values.