I was told during my PSI VCI class that the official answer was the beginning of the month, but that I was likely to see different interpretations of the expiration.
In practice, I know my LDS will fill to the end of the stickered month, so if I'm diving with them, I take my time. If I'm diving somewhere else, I'll just get around to doing my inspections to avoid any potential annoyance. (Last time, I did a dozen cylinders on a Tuesday night so I could get them filled on Wednesday for a dive trip leaving Thursday, and thanks to my TiVo, I didn't even miss House. :biggrin
In practice, I know my LDS will fill to the end of the stickered month, so if I'm diving with them, I take my time. If I'm diving somewhere else, I'll just get around to doing my inspections to avoid any potential annoyance. (Last time, I did a dozen cylinders on a Tuesday night so I could get them filled on Wednesday for a dive trip leaving Thursday, and thanks to my TiVo, I didn't even miss House. :biggrin