Irrespective of the length of time required to calculate one hash, how many hash operations are required to produce one Bitcoin?
These charts show the approximate network hash rate on the left axis: http://bitcoin.sipa.be/
We know the network adjusts for 25 new bitcoins per 10 minutes.
Together this provides enough info to give an approximate answer to your question:
hashes per bitcoin = (network hash rate) / (25 BTC per 10 minutes) = (180 * Th / s) / (25 * BTC / (600 * s) ) = 180 * 600 / 25 * Th / s / BTC * s = 2,700 Th / BTC = 2,700,000,000,000,000 h/BTC
A good and simple website to calculate how much bitcoin can be created with what machine can be found at: http://www.alcula.com/calculators/finance/bitcoin-mining/
Difficulty changes regularly, but there are calculators that take all current factors into account:
As of today (17 Jan 2017): a theoretical 1,581 TH/s (equivalent of running a hundred Antminer S9's) will return 1 BTC in a day.
Tomorrow, it will be different.