The local Class C closes at a certain time. When it does it reverts to E/G (haven't verified which in the green book) and you treat it like an uncontrolled field. So I'm returning from a destination around the time the controllers go home, which will have me transitioning/descending through the Charlie, and I pull up the ATIS when I'm about 50nm out and it broadcasts as expected. "...report you have information Sierra." I stop monitoring ATIS and continue on. I get to about 20-25 out, and the broadcast is now. "[Airport] automated weather observation system [weather info]. The tower is open from [time] local to [time] local. Common Traffic Advisory Frequency and pilot controlled lighting is [tower frequency]." I had the Approach Frequencies dialed in for a while, and heard no one talking at all prior to the ATIS broacast and after the AWOS broadcast. OK, I don't need to talk with anyone, they all went home. It's AWOS, not ATIS. I'm just above the Charlie, but right at the outer ring and call up on Tower/CTAF like I would with an uncontrolled field I'd be passing by: "[Airport] [Tail Number] is 10 miles [direction] at [altitude] and will be transitioning and descending the Charlie from [direction] to [direction] crossing just [direction] of the field [Airport]." I get no response on frequency and continue along. I've now descended into the charted airspace and am on an extended center line of one of the runways when I hear a transmission on CTAF: "Charlie Airspace Radar services are terminated, for advisories or flight following contact center on [frequency]." Wait. They already announced on ATIS it as AWOS and said the tower/approach was closed. What gives? Well ATIS gets updated 7 minutes before the hour and I was hitting the outer ring and into the airspace about 2 minutes prior to close. They don't update the ATIS for the seven minutes the Class C Services remain open, and flip it to AWOS at hh:53 rather than hh:00. I'm 100% sure that tower heard me on frequency and just said "screw it we are out of here in 2 minutes, no need to provide services when that guy is the only one in the airspace." Technically, I violated for about 2 minutes, but it could have been 7 and could have caused a PD if there had been arrivals. There are a couple late flights that do arrive just before and just after closing time. So check your clocks to be sure the Airspace isn't still open.