Date and time values can be stored with either the DATETIME or SMALLDATETIME data type. The difference between the two is that SMALLDATETIME supports a smaller range of dates and does not give the same level of precision when accounting for time. The DATETIME data type can hold values from January 1st of 1753 to December 31st of 9999. The time is stored to the 1 three hundredths of a second and each value takes up 8 bytes of storage. The SMALLDATETIME data type can hold values between January 1st 1900 and June 6th of 2079. The time is tracked to the minute and each value takes up 4 bytes of storage. The majority of business applications can live happily with SMALLDATETIME, however, if you are in an environment where each second matters or you need to make estimates to the distant future (or past) then you have to resort to DATETIME. If you fail to specify the time when inserting a value into a DATETIME or SMALLDATETIME column, a default of midnight is used. If you fail to specify the date portion the default of January 1, 1900 is used.
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