Java: Insert into a table datetime data

According to the error description, you are inserting an incorrect type into the database. See JDBC to MSSQL. You should convert Calendar to Timestamp.

Try using:

PrepareStatement statement     = connection.prepareStatement("INSERT INTO Companies CreatedOn VALUES(?)");java.sql.Timestamp timestamp = new java.sql.Timestamp(cal.getTimeInMillis());statement.setTimestamp(1, timstamp);int insertedRecordsCount = statement.executeUpdate();

First of all, do NOT use string concatenation. Have you ever heart about SQL injection?

Correct way how to do that is to use prepared statement:

Idea is you define statement with placeholders and than you define value for those placeholders.

See @Taky's answer for more details.

dateFormat#format this method returns formatted string not Date object. Database field is DateTime and it is expecting java.sql.Timestamp to be inserted there not String according to docs.

To conform with the definition of SQL DATE, the millisecond values wrapped by a java.sql.Date instance must be 'normalized' by setting the hours, minutes, seconds, and milliseconds to zero in the particular time zone with which the instance is associated.

Try java.sql.Timestamp object instead of String in query and I'd recommend you to use PreparedStatement.