'Spring forward or fall back,” said Simon during a lull in the conversation.

'What?”

'Spring forward or fallback spring. You know – DST.”

It's how Simon's Mum would remember the onset of daylight saving – setting her clock forward one hour during summer time and back one hour in autumn – all to make better use of natural daylight. Remember how daylight saving would make the farmers grumble.

Here in New Zealand daylight saving time begins at 2am on Sunday, September 30. Clocks should be set forward an hour – darker later in the morning and lighter later into the evenings for barbeques and beaches. Daylight saving will end in New Zealand at 2am on Sunday April 7 next year.

During the daylight savings months we are on New Zealand daylight time which is one hour ahead of New Zealand standard time.

New Zealand first observed daylight saving time in 1927 although the dates and time difference were changed several times over the following years. But in 1946 when New Zealand summer time - 12 hours rather than 11 hours and 30 minutes in advance of GMT was adopted as New Zealand standard time - daylight saving time was effectively discontinued.

Daylight saving was trialed again in 1974, and introduced in 1975.

Germany switched to DST in 1916. It became the first country in the world to use DST on a national level. However, the town of Thunder Bay in Ontario, Canada implemented DST already in 1908.

US inventor and politician Benjamin Franklin first proposed the concept of DST in 1784, but modern Daylight Saving Time was first suggested in 1895. At that time, George Vernon Hudson, an entomologist from New Zealand, presented a proposal for a 2-hour daylight saving shift.

Less than 40 percent of countries in the world use DST.

Some studies show that DST could lead to fewer road accidents and injuries by supplying more daylight during the hours more people use the roads. Other studies claim that people's health might suffer due to DST changes.

DST is also used to reduce the amount of energy needed for artificial lighting during the evening hours. However, many studies disagree about DST's energy savings, and while some studies show a positive outcome, others do not.

Not Always 1 Hour

Today clocks are almost always set 1 hour back or ahead.

However, on Lord Howe Island, Australia, clocks are set only 30 minutes forward from LHST (UTC+10:30) to LHDT (UTC+11) during DST.

30 and 45 minute time zones

Throughout history, there have been several variations, like half adjustments (30 minutes) or double adjustment (2 hours). Adjustments of 20 and 40 minutes have also been used.