A CARJ CREW DEPARTED MCN PRIOR TO THEIR RELEASE TIME.

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DEPARTING FROM MCN AT XA00. IFR FLT PLAN MCN DIRECT ATL. WE WERE RUNNING ABOUT 15 MINS BEHIND SCHEDULE DUE TO MAINT RELEASING ACFT 5-10 MINS LATE AND SIGNIFICANT WX CHANGE FROM DEP ARPT AND ALTERNATE ARPT. REQUIRED A RE-RELEASE/NEW RELEASE FROM FLT CTL. ON TAXI OUT; PICKED UP CLRNC FROM MACON APCH. WE WERE CLRED TO ATL AS FILED TO 5000 FT; EXPECT 12000 FT 10 MINS AFTER DEP; SQUAWK XXXX WITH A RELEASE TIME OF XA18Z AND A VOID TIME XA54Z. CURRENT TIME WAS ACCORDING TO OUR CLOCKS XA45Z. RAN CHKLISTS NORMAL; CALLED CTAF TO INFORM OF OUR DEP OFF OF RWY 5. TIME ON THE CLOCK (CAPT'S SIDE) WAS THE RELEASE TIME OF XA18. AIRBORNE OUT OF APPROX 2000 FT MSL; TURNING ON COURSE; CONTACTED APCH. APCH THEN ASKED US IF WE KNEW OUR RELEASE TIME. ACKNOWLEDGED TO ATC. WE INSPECTED THE CLOCKS AND WATCHES AND FOUND CAPT'S CLOCK WAS ABOUT 45 SECONDS FASTER THAN THE FO'S CLOCK. THE FO'S CLOCK WAS ABOUT 2 MINS FASTER THAN THE FO'S WATCH. BESIDES ATC ASKING US ABOUT OUR RELEASE TIME; FOUND WE HAD LEFT MCN IFR ABOUT 2-3 MINS BEFORE OUR RELEASE TIME. THERE WERE NO TFC CONFLICTS ENCOUNTERED OR OTHER HAZARDS ON DEP. WE REALIZED THE SEVERITY OF OUR ERROR AND ATC DID NOT REQUEST ANY INFO FROM US. TIMES UTC OR LOCAL SHOULD BE EMPHASIZED MORE THAN THEY ARE WHEN PICKING UP CLRNCS FROM UNCTLED FIELDS.