It is 9 hours.
9am, 10am, 11am, 12pm, 1pm, 2pm, 3pm, 4pm, 5pm. 8 hours.
3pm to 10pm is 7 hours.
between 12pm and 3pm
12pm to 7pm is a span of 7 hours.
24 of course !
12pm PST is 3pm EST reference: http:/www.timeanddate.com
Noon is at 12 pm so afternoon is any time after 12pm and before about 6pm. This means 3pm is mid-afternoon and anything between 12pm and 3pm can be early afternoon. However if someone asked me to call the in early afternoon, I would call the between 12pm and 1.30pm because this is the first quarter of the afternoon.