Narrative:

Crew scheduling reassigned me to operate [another flight] instead of deadheading. I preflighted the aircraft; briefed with my captain and performed checklists. The line of stormy weather from the west started to move over bwi. The weather had lightning associated which in turn closed the ramp. The ramp closure delayed our departure from the gate. After a while we pushed back from the gate and were instructed to taxi to the deice pad by runway 15R and park due to the fact that our route to [our destination] was closed. During this time my captain and I were contacting dispatch; ground control and clearance delivery to help find a new route to help us depart bwi as soon as possible. I calculated my duty day in my mind and thought that I was legal due to the fact that I believed I could be two hours extended due to irregular operations. I received messages from dispatch concerning our route via ACARS. We received our new clearance and taxied to 33L. I sent messages to dispatch concerning our fuel status and received amendments to our dispatch release for fuel planning. We departed 33L at bwi about an hour and 20 minutes after we pushed. We arrived [at our destination]; parked at the gate and shutdown the aircraft. I looked at my crew board and reviewed my flight time and duty times and realized that the calculations I made for my flight duty times in my head were completely wrong. I thought the latest wheels up time was extendable for two hours due to irregular operations. I was totally wrong. I found the far 117 chart on flight duty times and was horrified that I exceeded my max duty time. I was never contacted by crew scheduling via ACARS or cell message during my time on the aircraft. I have learned the hard way to be extremely mindful of my flight duty limits and triple-check the charted limits against my scheduled flying.I should have called crew scheduling to help with any confusion over flight duty limits. I got distracted with coordinating ATC reroutes and inclement weather. I should always compare the far 117 chart to my scheduled flying and understand how to calculate it and understand how to apply the correct extension if needed.

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Original NASA ASRS Text

Title: B737 First Officer reported unknowingly exceeding FAR 117 maximum duty day limits.

Narrative: Crew Scheduling reassigned me to operate [another flight] instead of deadheading. I preflighted the aircraft; briefed with my Captain and performed checklists. The line of stormy weather from the west started to move over BWI. The weather had lightning associated which in turn closed the ramp. The ramp closure delayed our departure from the gate. After a while we pushed back from the gate and were instructed to taxi to the deice pad by Runway 15R and park due to the fact that our route to [our destination] was closed. During this time my Captain and I were contacting Dispatch; Ground Control and Clearance Delivery to help find a new route to help us depart BWI as soon as possible. I calculated my duty day in my mind and thought that I was legal due to the fact that I believed I could be two hours extended due to irregular operations. I received messages from Dispatch concerning our route via ACARS. We received our new clearance and taxied to 33L. I sent messages to Dispatch concerning our fuel status and received amendments to our Dispatch Release for fuel planning. We departed 33L at BWI about an hour and 20 minutes after we pushed. We arrived [at our destination]; parked at the gate and shutdown the aircraft. I looked at my Crew board and reviewed my flight time and duty times and realized that the calculations I made for my flight duty times in my head were completely wrong. I thought the latest wheels up time was extendable for two hours due to irregular operations. I was totally wrong. I found the FAR 117 Chart on Flight Duty Times and was horrified that I exceeded my max duty time. I was never contacted by Crew Scheduling via ACARS or cell message during my time on the aircraft. I have learned the hard way to be extremely mindful of my flight duty limits and triple-check the charted limits against my scheduled flying.I should have called Crew Scheduling to help with any confusion over Flight Duty Limits. I got distracted with coordinating ATC reroutes and inclement weather. I should always compare the FAR 117 Chart to my scheduled flying and understand how to calculate it and understand how to apply the correct extension if needed.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.