My Honda user manual says to operate the AC once a week but
doesn't say how long. The car is in storage and every week I go
start the car and operate the AC for half a minute and shut it off.

Sometime it's so cold outside that the AC will not turn on. I'm unsure
if it's empty of freon or it's just too cold outside, 20-degree F. How
long should we start a car and operate the A/C in order to meet the
factory requirements?

TIA, `93 Honda Accord lx