Dmitry, rather than concatenating values, use parameterized SQL.

tDatetime=datetime()
lcSQL="update MyTable Set DateTimeColumn = ?tdatetime where Pk = ?nPk"

Apart from taking care of the conversions for you, in SQL Server 7 and later a parameterized query like this will be cached at the server, giving significant improvement benefits.

The other advantage is that parameters prevent SQL Injection. The concatenated examples in this thread are all wide open to injection if a hacker can sneak a quote character into the parameter followed by their own SQL command that could be a SELECT * to steal your customer list or a DROP if they are malicious. You can write code to watch for quotes and other injection attempts, but using parameters makes it a complete non-event.

FWIW for those who have not encountered SQL Injection, here's a simple example of concatenated SQL:

"SELECT * FROM members WHERE username = "'+lcusername+"'"

If the hacker can enter their username as bob'; DROP table members; -- then the SQL becomes

SELECT * FROM members WHERE username='bob'; DROP table members; --'

and you get the idea. yes you can write code to prevent use of quote characters etc but this cannot occur at all if you use parameters.