''unfortunately this page got deleted by accident, this version is restored from [https://web.archive.org/web/20150318062024/http://kernelnewbies.org/y2038], but most of the formatting is still missing.

== The year 2038 problem ==

All 32-bit kernels to date use a signed 32-bit time_t type, which can only represent time until January 2038. Since embedded systems running 32-bit Linux are going to survive beyond that date, we have to change all current uses, in a backwards compatible way.

=== User space interfaces ===
We will likely keep the 32-bit time_t in all user space interfaces that currently use it, but add new interfaces with a 64-bit timespec or another type that can represent later times. Most importantly that impacts system calls, but also specific ioctl commands and a few other interfaces. User space programs have to be recompiled to use the new interfaces, and the policy whether to use the old or the time time is left to the C library. While that policy is a complex topic itself, we don't cover it here.

==== System calls ====

System calls have been moved out [[:y2038/syscalls:]], that page is rather outdated, newer information is available at https://lwn.net/Articles/643234/

=== File systems ===
Each file system stores its file modification times in its own format on disk, and a lot of them have the same problem.

|| file system || time type || expiration year ||
|| 9p (9P2000) || unsigned 32-bit seconds || 2106 ||
|| file system || time type || expiration year ||
|| 9p (9P2000) || unsigned 32-bit seconds || 2106 ||
|| 9p (9P2000.L) || signed 64-bit seconds, ns || never ||
|| adfs || 40-bit  cs since 1900 || 2248 ||
|| affs || u32 days/mins/(secs/50) || 11760870 ||
|| afs || unsigned 32-bit seconds || 2106 ||
|| befs || unsigned 48-bit seconds || never ||
|| bfs || unsigned 32-bit seconds || 2106 ||
|| btrfs || signed 64-bit seconds, 32-bit ns || never ||
|| ceph || unsigned 32-bit second/ns || 2106 ||
|| cifs (smb) || 7-bit years since 1980 || 2107 ||
|| cifs (modern) || 64-bit 100ns since 1601 || 30328 ||
|| coda || timespec ioctl || 2038 ||
|| cramfs || fixed || 1970 ||
|| efs || unsigned 32-bit seconds || 2106 ||
|| exofs || signed 32-bit seconds || 2038 ||
|| ext2 || signed 32-bit seconds || 2038 ||
|| ext3 || signed 32-bit seconds || 2038 ||
|| ext4 (good old inodes) || signed 32-bit seconds || 2038 ||
|| ext4 (new inodes || 34 bit seconds / 30-bit ns (but broken) || 2038 ||
|| f2fs || 64-bit seconds / 32-bit ns || never ||
|| fat || 7-bit years since 1980, 2s resolution || 2107 ||
|| freevxfs || unsigned 32-bit seconds/u32 microseconds || 2106 ||
|| fuse || 64-bit second/32-bit ns || never ||
|| gfs2 || u64 seconds/u32 ns || never ||
|| hfs || u32 seconds since 1904 || 2040 ||
|| hfsplus || u32 seconds since 1904 || 2040 ||
|| hostfs || timespec || 2038 ||
|| hpfs || unsigned 32-bit seconds || 2106 ||
|| isofs || 'char' year since 1900 (fixable) || 2028  ||
|| jffs2 || unsigned 32-bit seconds || 2106 ||
|| jfs || unsigned 32-bit seconds/ns || 2106 ||
|| logfs || signed 64-bit ns || 2262 ||
|| minix || unsigned 32-bit seconds || 2106 ||
|| ncpfs || 7-bit year since 1980 || 2107 ||
|| nfsv2,v3 || unsigned 32-bit seconds/ns || 2106 ||
|| nfsv4 || u64 seconds/u32 ns || never ||
|| nfsd || unsigned 32-bit seconds/ns || 2106 ||
|| nilfs2 || u64 seconds/u32 ns || never ||
|| ntfs || 64-bit 100ns since 1601 || 30828 ||
|| ocfs2 || 34-bit seconds/30-bit ns || 2514 ||
|| omfs || 64-bit milliseconds || never ||
|| pstore || ascii seconds || 2106 ||
|| qnx4 || unsigned 32-bit seconds || 2106 ||
|| qnx6 || unsigned 32-bit seconds || 2106 ||
|| reiserfs || unsigned 32-bit seconds || 2106 ||
|| romfs || fixed || 1970 ||
|| squashfs || unsigned 32-bit seconds || 2106 ||
|| sysv || unsigned 32-bit seconds || 2106 ||
|| ubifs || u64 second/u32 ns || never ||
|| udf || u16 year || 2038 ||
|| ufs1 || unsigned 32-bit seconds || 2106 ||
|| ufs2 || signed 64-bit seconds/u32 ns || never ||
|| xfs || signed 32-bit seconds/ns || 2106 ||

=== Tasks ===

The task list is for people that want to get involved, there will be many more tasks over time, so this is just a starting point. In the end, we should remove all instances of 'time_t', 'timespec' and 'timeval' from the kernel.

==== Trivial tasks ====

Find a driver using time_t/timespec/timeval internally and convert it to ktime_t/timespec64, examples:

 * drivers/firewire/core-cdev.c
 * drivers/firewire/nosy.c
 * drivers/hv/hv_util.c
 * drivers/infiniband/hw/nes/
 * drivers/misc/ibmasm/ibmasm.h
 * drivers/net/wireless/atmel.c
 * drivers/ide/pdc202xx_new.c
 * fs/fuse/dir.c
 * drivers/scsi/pmcraid.c

==== Small tasks ====

Find a driver using time_t/timespec/timeval internally and convert it to ktime_t/timespec64, examples:

 * drivers/block/sx8.c
 * drivers/char/ipmi/ipmi_ssif.c
 * drivers/char/mmtimer.c
 * drivers/cpufreq/speedstep-lib.c
 * drivers/hsi/clients/cmt_speech.c
 * drivers/media/platform/vivid/
 * drivers/net/hamradio/baycom_ser_fdx.c

==== Medium tasks ====

 * Modify an ioctl interface in a driver to support both 32- and 64-bit time interfaces, examples:

  * drivers/usb/misc/usbtest.c

 * Convert the internal timekeeping in fs/nfsd

 * Convert all 'struct key' users (time_t)

 * fix all uses of timeval in drivers/scsi/bfa


==== Advanced tasks ====

 * Change the on-disk layout of a broken file system to optionally support longer time stamps

 * Port a small C library (uClibc, newlib, ...) to optionally use 64-bit time_t and build an embedded distribution (openembedded, openwrt, buildroot, ...) with this.

 * start migrating the times in 'struct inode' and 'struct 'kstat' to separate 64-bit second + 32-bit nanosecond fields.

==== Tasks later in the project ====

 * Hook up all 32-bit architectures to use the new system calls

 * Introduce a Kconfig symbol to disable all code that has not yet been converted at compile time.