math challenge

Week of April 14 - 20, 1997

Fun With Bubble-Boy

John is living and working in a hermetically sealed bubble, investigating where socks go to live after visiting the dryer. His sense of in-built time is slowly fading. He has two clocks. One is fast, with 1 minute being recorded as 1 minute, 30 seconds. The other is slow, with 1 minute being recorded as 30 seconds.

John entered the bubble on December 1, 1990 at 00:01:00. His two clocks were correct at that time.

How many times during the month of December will both clocks be correct AT THE SAME TIME? Both are 12-hour clocks.

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