Three seconds to say I love you, three hours to explain it, and a lifetime to prove it.

说“我爱你”只需三秒钟，解释“我爱你”需要三个小时，证明“我爱你”需要一生。

youdao

It takes three seconds to say "I love you", three hours to explain it, and a lifetime to prove it.

“我爱你”，说出来要三秒钟，说明它要三小时，却需要一辈子去证实。

youdao

"It took him about three seconds to realize the impact of what happened.

VOA: standard.2009.05.22

That is, it doesn't take one second to go the first, and then two seconds to go to the second, and three seconds to go to third.

就是说,不是第一秒到第一排,第二秒第二排,第三秒第三排这样

耶鲁公开课 - 生物医学工程探索课程节选

He hit two free throws in the final seconds to give Los Angeles an eighty-three to seventy-nine victory.

VOA: special.2010.06.25

Allow two or three seconds to go by before gradually changing your body language to (more or less) reflect that of the other person.

FORBES: President Obama, Congress, and the Body Language of Negotiation

Mr. Sanchez spiked the ball with three seconds remaining to set the stage for Mr. Folk.

WSJ: Folk's 32-Yard Field Goal Sends Jets Past Colts

The St Malachy's athlete needed to beat three minutes 40 seconds to guarantee a trip to Melbourne next March.

BBC: SPORT | Athletics | Turnbull's Belfast race cancelled