The clocks go forward by one hour at 2am on Sunday morning on the last weekend in April, marking the beginning of zomertijd (summer time), internationally known as daylight-saving time. The Netherlands scrapped the principle of summer time in 1939 but reintroduced it in 1977 at the height of the oil crisis. Without this changing of the clock, it would start getting light at 3.30am by mid-June. The clocks go back again in the last weekend in October (wintertijd).