It’s that time of year again and at 2 a.m. Sunday, folks will need to ‘spring forward’ by moving their clocks one-hour ahead.

This year’s start to Daylight Saving Time marks the 100th year since it was first introduced in the US.

“The aim of this is to make use of daylight longer into the evening by starting daylight later in the morning,” states an article by Calendarpedia. “Introduced for the first in 1918 during World War I for just one summer, Daylight Saving Time was used only intermittently and only in some states until World War II, when it was reintroduced nationwide and year-round as ‘War Time.’”

Not every state practices Daylight Saving Time.

“Sun-baked Arizona and Hawaii refuse to change their clocks. Both Massachusetts and Maine have considered getting off DST, but haven’t scrapped the whole thing quite yet,” states a March article from Big Think.

Most cell phones will automatically change, but don’t forget to manually get the rest set forward.

The clocks will “fall back” the first Sunday in November.