21 times. Between 12 midnight and 1am the hands don’t cross. Then between 1am and 2am the hands cross once, just after 1:05. During each hour the hands cross once until 11am. So that’s 10 times. The slightly unexpected thing is that between 11 o’clock and 1 o’clock the minute hand passes over the hour hand only once – at midday. From 1pm to 11pm the hands again cross 10 times. Then in the final hour they don’t cross. So that’s a total of 21 times.