I have no idea what happened to the GPS timing on fb1, but it seems like the issue was coincident with the power glitch on Monday.
As was noted by Koji above, the GPS time kernel interface was off by a year, which was causing the frame builder to write out files with the wrong names. fb1 was using DAQD components from the advligorts 3.3 release, which used the old "symmetricom" kernel module for the GPS time. This old module was also known to have issues with time offsets. This issue is remniscent of previous timing issues with the DAQ on fb1.
I noted that a newer version of the advligorts, version 3.4, was available on debian jessie, the system running on fb1. advligorts 3.4 includes a newer version of the GPS time module, renamed gpstime. I checked with Jonathan Hanks that the interfaces did not change between 3.3 and 3.4, and 3.4 was mostly a bug fix and packaging release, so I decided to upgrade the DAQ to get the new components. I therefore did the following
updated the archive info in /etc/apt/sources.list.d/cdssoft.list, and added the "jessie-restricted" archive which includes the mx packages: https://git.ligo.org/cds-packaging/docs/-/wikis/home
removed the symmetricom module from the kernel
sudo rmmod symmetricom
upgraded the advligorts-daqd components (NOTE I did not upgrade the rest of the system, although there are outstanding security upgrades needed):
sudo apt install advligorts-daqd advligorts-daqd-dc-mx
loaded the new gpstime module and checked that the GPS time was correct:
sudo modprobe gpstime
restarted all the daqd processes
sudo systemctl restart daqd_*
Everything came up fine at that point, and I checked that the correct frames were being written out.