This year, DST will start on the second Sunday of March and end on the first Sunday of November. Canada and some of the Caribbean countries are also extending their DST period to match that of the US.
The list of the affected timezones can be seen at TimeAndDate.com.
These changes affect computer systems that operate with the timezones affected by the new rules. If you work with accounts using the affected timezones, you likely need to take action to correctly interpret dates and times when using EWS.
To address this problem many software vendors have released patches for their products. The following list provides links for articles covering popular software products: