Narrative:

During preflight planning discovered this was the third airplane assigned to the flight. Arrived at the aircraft and discussed two MEL (minimum equipment list) items which we reviewed together and called maintenance out to clarify an item. All four pilots handled and reviewed the logbook during this discussion. We all briefed the ETOPS (extended twin operations) signoff and agreed it was done and in the book. The boarding was slightly delayed so there was no pressure to get things done quickly. After about two hours into cruise dispatch sent a message asking if the ETOPS signoff was in the logbook. I checked it and found that there was indeed an entry and it was the correct date but saw that the departure station was ZZZZ. This means that the signoff was for the previous leg which was the day before. The day before; in the other hemisphere. We all were looking for an ETOPS date and we all saw what we expected to see. At that point we were not in ETOPS airspace and worked out a routing with dispatch that avoided ETOPS airspace entirely and secured the clearances with ATC (air traffic control). Shortly after dispatch told us that the maintenance department wanted us to return the airplane to ZZZ. We asked to divert to minimize the delay to the passengers but were told to return to ZZZ. The return to ZZZ required and overweight landing at 485;000 lbs (max landing weight is 460;000 lbs); so ATC was advised. All checklists were complete and an uneventful landing was made.I think all pilots expected to see an ETOPS signoff dated [the same day] and that is exactly what we saw. We should have reviewed the entry more carefully. There was no reason as we were not rushing to depart; we just missed the fact that the last leg originated in the other hemisphere.I need to inspect the logbook entries more carefully and make sure I know where the previous leg originated; especially when a change of equipment is involved. I never suspected the date line issue would cause such a problem but it happened.

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Original NASA ASRS Text

Title: B777-200 reported returning to departure airport after inadvertently departing without proper ETOPS sign-off in logbook.

Narrative: During preflight planning discovered this was the third airplane assigned to the flight. Arrived at the aircraft and discussed two MEL (Minimum Equipment List) items which we reviewed together and called Maintenance out to clarify an item. All four pilots handled and reviewed the logbook during this discussion. We all briefed the ETOPS (Extended Twin Operations) signoff and agreed it was done and in the book. The boarding was slightly delayed so there was no pressure to get things done quickly. After about two hours into cruise Dispatch sent a message asking if the ETOPS signoff was in the logbook. I checked it and found that there was indeed an entry and it was the correct date but saw that the departure station was ZZZZ. This means that the signoff was for the previous leg which was the day before. The day before; in the other hemisphere. We all were looking for an ETOPS date and we all saw what we expected to see. At that point we were not in ETOPS airspace and worked out a routing with Dispatch that avoided ETOPS airspace entirely and secured the clearances with ATC (Air Traffic Control). Shortly after Dispatch told us that the maintenance department wanted us to return the airplane to ZZZ. We asked to divert to minimize the delay to the passengers but were told to return to ZZZ. The return to ZZZ required and overweight landing at 485;000 lbs (max landing weight is 460;000 lbs); so ATC was advised. All checklists were complete and an uneventful landing was made.I think all pilots expected to see an ETOPS signoff dated [the same day] and that is exactly what we saw. We should have reviewed the entry more carefully. There was no reason as we were not rushing to depart; we just missed the fact that the last leg originated in the other hemisphere.I need to inspect the logbook entries more carefully and make sure I know where the previous leg originated; especially when a change of equipment is involved. I never suspected the date line issue would cause such a problem but it happened.

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.