Daylight Savings Time starts at different dates in different parts of the world. Places in North America generally starts it on the second Sunday of March (i.e. last sunday), whereas European countries do it on the last Sunday of March (i.e. three weeks later this year).
Because of this, if you're in a region that hasn't fiddled with their clocks this spring, it's important to keep this one hour difference in mind when setting reminders for streams and such.