He means that a datetime is a number[^], and as such, is neutral. To quote; SQL Server uses 8 bytes to store the datetime data type. The first 4 bytes make up an integer value that represents the number of days since January 1, 1900. The second 4 bytes are an integer value that represents the number of milliseconds since midnight. When you send a date to the database, do you convert it to a string that get's included in your (text) command? If so, then you can get errors converting from/to the wrong format. If you send it as a number, then it will be interpreted as a "days past since date 1"-number. Try casting a date to float/integer, and see what happens :)
I are troll :)