Also, do not forget that every function in the body exhibits a circadian cycle. Likewise, alcohol metabolism:
This is from an old study, from the times when it was OK to recruit some college freshmen to drink alcoholic beverages in the name of science. This is a record of a diurnal rhythm in alcohol clearance, I believe (I cannot find the original paper I swiped this image from a long time ago).
It shows why we can drink more in the evening than at other times of day. You can save some serious money by downing a single shot at dawn, according to this graph.
So, at what time of day/night did the cops stop you to give you a breathalyzer test?