为什么从DATE到VARCHAR的强制转换是非确定性的？

In trying to add a computed column to a SQL Server table, I've found that casting a column with a DATE type directly to a VARCHAR is considered non-deterministic. However, If I pull out the individual parts of the date and cast them individually then everything is fine. I can't think of a reasonable explaination for why the cast directly from DATE to VARCHAR would be non-deterministic. Does anyone have an explanation?In trying to add a computed column to a SQL Ser