There is only one proper way to insert dates into SQL Server. Use a region-independent format. You should only worry about the region when displaying dates, not storing them.
For storing dates, the ISO standard is “yyyymmdd”.
For date and time, it’s “yyyymmdd hh:mm:ss” (24-hour time).
Use single quotes around the date string.
If possible, always store dates in UTC time (universal time, i.e. Grenwich mean time).
For example, to insert 8 Dec 2006:
INSERT INTO tablename (datefield) VALUES (‘20061208’)
To insert 8 Dec 2006, 5:30pm:
INSERT INTO tablename (datefield) VALUES (‘20061208 17:30:00’)
Actualy,
When inserting anything in sql, you should use parameters, for security reasons. Also, this way you will not have problems with dates or other data types.