Daylight Saving Time (DST) represents advancing of clocks so that the afternoons have more daylight than the mornings. Typically clocks are adjusted forward one hour near the start of spring and are adjusted backward in autumn. DST is first introduced in 1907 and ever since several countries are following it. In European Union, DST is called Summer Time (ST).

So, if you were born in a country during the months when the DST is observed, your birth time should be adjusted accordingly. Suppose you were born in June at 5.00 pm in USA. Till the end of 2006, USA observed DST from first Sunday in April till last Sunday in October, so your recorded birth time would have been advanced by 1 hr. This 1 hr should be deducted from your recorded time of birth, and hence your actual (standard) time of birth will be 4.00 pm. If you were born during the months when the DST is not observed, then you need not adjust your recorded birth time.