Interesting question.
Were you thinking that we should say �how many�?
Of course we measure time in seconds, minutes, hours, weeks, etc.
We can count those units.
We cannot count time, but we can count the units we use when we measure time.
Similarly, we say �How much money do we have?�, but we do not say, �How many money do we have.�
We do say �How many (coins/notes) do we have.�
Why?
Time and money expressions show things which we think of as �volume�, and that is why we say �much�, when we usually use �many� with things we count.
Your question gave me an idea for a lesson on: much/many/exceptions to the rule.
Thanks.