Why Does Ice Hockey Have Three Periods?

Because ice hockey is female?

They used to have four, but the ZAMBONI® kept running out of gas, so they had to shorten it to three.

It has been said that the reason is for ice resurfacing,the surface will remain in good shape fo 20 minutes then it is resurfaced and again at the end of the 2nd period.

I Know Is That Hockey Has 3 Periods Each One Lasting 20 minutes.. Equaling 1Hour..  I Don't Watch It Or Know Much Else About It Except They Always Get In Fights,, And Lots Of Players Are Missing Teeth..  They Have On Tons Of Protection Because Of Hockey Pucks Flying Around At Warp Speed; And Those Sticks Whacking The Puck At Warp Speed lnto The Goal..  I've Seen Some Wicked Hockey Fights On "You Tube".. It's A Very Violent Game. I Would Not Want To Be Gouged In The Face With One Of Those Blades Either.. That Stanley Cup Is Grand Looking..Do You Watch Hockey?? Is That Why You Asked? I'm A Sick Wench.. I'd Watch For The Fights I Guess... The Puck Goes Too Fast For Me To Watch.