Clocks are advanced by one hour during the very early morning at the beginning of DST.
When DST ends, clocks are set back (as if to repeat one hour) during the very early morning. Specific times vary.
Daylight Saving Time (DST) or Summer Time (ST) is a time to time keep during summer. During the summer months, the sun stays visible for a longer time, and sunset happens late in the day. For this reason, certain countries advance the time by one hour near the start of summer, and put it back one hour during autumn.