On Sunday, March 8th at 2AM, the U.S. will start daylight saving time. This means people in the U.S. will set their clocks forward by one hour (2AM becomes 3AM), and the change will push sunsets later.
The U.S. starts daylight saving time three weeks before Europe (on March 29th). Thus, for the next three weeks, there is one less hour between the US and Europe (5 hours instead of 6 hours). For example, during standard time 9am ET = 3pm CET but during DST 9am ET = 2pm CET.
As a bonus, over the next three weeks, US filers will have one extra hour to submit their documents to European based agencies. For example, US filers have until 7pm ET to submit their documents to WIPO in Switzerland to receive the same-day filing date.