During our current spate of snow, rain, freezing rain the dreaded “wintry mix” and more snow, any sign of spring would be a welcome one.

One herald of the hypothetical warmer days ahead arrived at 2 a.m. when most of the country turned their clocks ahead one hour to daylight-saving time.

Many have already noticed that the days are staying lighter later, thanks to the normal course of the Earth's movements in relation to the sun, but daylight-saving time accelerates the process.

That process comes to a head at 6:45 p.m. March 20 with the arrival of the vernal equinox, according to James Clem, assistant professor of physics at Grove City College.

The vernal equinox has an astronomical significance, he said, because it corresponds to the date (and time) when the sun crosses the celestial equator, an imaginary line in the sky directly over equator, traveling south to north.

On that day, almost all points on the Earth will experience a nearly equal number of daylight and nighttime hours (i.e., 12 hours of day and 12 hours of night — the term “equinox” literally translates as “equal night”).

“Many people, not just astronomers, have adopted the day the vernal equinox occurs as the 'first official day of spring' because it has a couple of consequences for people living in the northern hemisphere of Earth that are relevant to the seasonal change from winter to spring,” said Clem.

For example, he said, the sun rises earlier and sets later each day and follows a higher path in the sky giving rise to longer days and shorter nights.

This means more solar energy strikes the Earth's surface as the sun climbs higher in the sky and, combined with the longer daylight, leads to more efficient heating of the Earth's surface that can bring about an increase in air temperatures (i.e., an overall warming trend).

But it's a gradual process, warned Julie Snow, associate professor of geography, geology and environment at Slippery Rock University.

“In my mind, the sun's rays at 90 degrees hitting the equator is the vernal equinox,” said Snow.

“But that doesn't mean we won't get snow in April,” she said. “ It takes time for the planet to absorb that energy.”

“And the key is energy. We talk about temperature but temperature is a measure of kinetic energy,” said Snow.

Clem said, “Ancient cultures took notice of days such as the vernal equinox on their calendars because they were important for agricultural and religious/cultural reasons, among others.”

“Numerous ancient civilizations held the vernal equinox in great importance — these include the Egyptians, Persians, and Mayans to name a few,” he said.

For some, the vernal equinox was a time of celebration because it signaled that a time would be approaching when they could begin to plant crops and replenish their food supply, he added.

But Luke Fritz, the executive director of the USDA Farm Service Agency which administers federal farm programs in Butler County, said the county's 800 to 900 farmers are still more than a month away from actually getting into their fields.

“I'm sure some are starting seeds in greenhouses or purchasing fertilizer, seeds and pesticides or performing maintenance on their equipment,” said Fritz.

The vernal equinox is not just important to farmers. The fathers of the early Christian church used it to determine the date of Easter, said the Rev. Philip Farrell, episcopal vicar for Region Four of the Pittsburgh Diocese.

Farrell said, “The date of Easter is based on the resurrection of Jesus, three days after the crucifixion which occurred on Passover, but much debate arose when trying to fix this date annually.”

“Difficulty arises when trying to translate an 'immovable feast' from a lunar calendar to a Christian solar calendar,” said Farrell.

“And it grows tougher when dealing with two different calendars, the Julian and the Gregorian,” he said.

Finally, the Council of Nicaea in A.D. 325 placed Easter on the first Sunday following the first full moon after the vernal equinox.

Farrell said church tradition holds that this process was chosen to allow pilgrims to have ample moonlight to travel to the great Easter festivals of the day.

Easter can arrive as early as March 22 and as late as April 25, Farrell said. This year Easter is April 5, one day after the full moon following the vernal equinox.

But daylight-saving time is entirely a modern “invention” dating back to its first usage about 100 years ago, said Clem.

With the vernal equinox approaching, he said, “We know that the days will get longer and the nights shorter, and daylight-saving time was designed specifically to take better advantage of these longer days in efforts to conserve energy and better fit modern human schedules.

The days when we “spring forward” or “fall back” have been revised over the past several years and the dates vary from country to country. Currently, in the US daylight-saving time begins the second Sunday in March and ends the first Sunday in November (as determined by the Energy Policy Act of 2005) — lasting about eight months.

However, there have been times during the past century, when the begin/end dates have been different. One notable example, year-round daylight-saving time, was in effect for three years during World War II to help conserve energy for the war effort.

Interestingly, two states do not adopt daylight-saving times — Arizona and Hawaii.

While many welcome the tradition of “springing” forward, some people complain about the lost hour of sleep.

Kevin Wolfe, supervisor of the sleep center at Butler Memorial Hospital, said adjusting to the time change “is a little like traveling, sort of like jet lag.”

“I've read studies that say our circadian rhythms never adjust and others say your body adjusts within a week,” Wolfe said.

Wolfe said light suppresses melatonin, the hormone that controls sleep and waking cycles, so an hour's worth of extra light at the end of day can throw people out of whack.

To adjust, he said, “Go to bed a little earlier. No caffeine or alcohol and limit exercise in the hours before bedtime. Try to relax and wind down before bed.”