Fixes and mitigations

There is no single patch. Every layer that stored 32-bit seconds has to stop doing that, or be replaced before its horizon hits the deadline.

What works

64-bit time_t in the kernel, libc, and every public struct. This is the real fix. Overflow moves to a cosmological date.
Rebuild on a time64 ABI for 32-bit hardware that must stay 32-bit (Debian armhf, Yocto with BR2_TIME_BITS_64, glibc _TIME_BITS=64).
Widen columns and file formats: BIGINT, DATETIME, ext4 large inodes, XFS bigtime.
Replace unpatchable hardware on a schedule set by Backwards Risk, not by 2037 panic.

What only buys time

Unsigned 32-bit Unix time reaches 7 February 2106 and cannot represent dates before 1970. It is a valid tactic for a sealed logger that will be scrap by 2050. It is not a platform strategy.

What does not work

Assuming “we are 64-bit now” without reading schemas and firmware.
Changing display dates to look fresh.
Testing only date on the shell prompt.